sagemathgh-39990: Remove ability to conditionalize parts of the documentation
    
The PR sagemath#36495 introduced the ability to disable building parts of the
documentation based on some features. This was meant to help the
modularization project, but was never actually used.

On the other hand, it checks for *every* of the around 200 document the
presence of *every* feature, leading to quite a considerable overhead
for building the documentation. Thus this feature is reverted for now
(until it's actually needed and perhaps can be re-implemented in a
better way).

<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->



### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#39990
Reported by: Tobias Diez
Reviewer(s): Dima Pasechnik

Author: Release Manager

src/doc/ca/intro/conf.py

@@ -13,11 +13,6 @@
 from sage_docbuild.conf import release
 from sage_docbuild.conf import *  # NOQA
 
-
-for tag in feature_tags():
-    tags.add(tag)
-
-
 # Add any paths that contain custom static files (such as style sheets),
 # relative to this directory to html_static_path. They are copied after the
 # builtin static files, so a file named "default.css" will overwrite the

src/doc/de/a_tour_of_sage/conf.py

@@ -15,11 +15,6 @@
 from sage_docbuild.conf import release
 from sage_docbuild.conf import *  # NOQA
 
-
-for tag in feature_tags():
-    tags.add(tag)
-
-
 # Add any paths that contain custom static files (such as style sheets),
 # relative to this directory to html_static_path. They are copied after the
 # builtin static files, so a file named "default.css" will overwrite the

src/doc/de/thematische_anleitungen/conf.py

@@ -13,11 +13,6 @@
 from sage_docbuild.conf import release
 from sage_docbuild.conf import *  # NOQA
 
-
-for tag in feature_tags():
-    tags.add(tag)
-
-
 # Add any paths that contain custom static files (such as style sheets),
 # relative to this directory to html_static_path. They are copied after the
 # builtin static files, so a file named "default.css" will overwrite the

src/doc/de/tutorial/conf.py

@@ -13,11 +13,6 @@
 from sage_docbuild.conf import release
 from sage_docbuild.conf import *  # NOQA
 
-
-for tag in feature_tags():
-    tags.add(tag)
-
-
 # Add any paths that contain custom static files (such as style sheets),
 # relative to this directory to html_static_path. They are copied after the
 # builtin static files, so a file named "default.css" will overwrite the

src/doc/el/a_tour_of_sage/conf.py

@@ -13,11 +13,6 @@
 from sage_docbuild.conf import release
 from sage_docbuild.conf import *  # NOQA
 
-
-for tag in feature_tags():
-    tags.add(tag)
-
-
 # Add any paths that contain custom static files (such as style sheets),
 # relative to this directory to html_static_path. They are copied after the
 # builtin static files, so a file named "default.css" will overwrite the

src/doc/en/a_tour_of_sage/conf.py

@@ -13,11 +13,6 @@
 from sage_docbuild.conf import release
 from sage_docbuild.conf import *  # NOQA
 
-
-for tag in feature_tags():
-    tags.add(tag)
-
-
 # Add any paths that contain custom static files (such as style sheets),
 # relative to this directory to html_static_path. They are copied after the
 # builtin static files, so a file named "default.css" will overwrite the

src/doc/en/constructions/conf.py

@@ -13,11 +13,6 @@
 from sage_docbuild.conf import release
 from sage_docbuild.conf import *  # NOQA
 
-
-for tag in feature_tags():
-    tags.add(tag)
-
-
 # Add any paths that contain custom static files (such as style sheets),
 # relative to this directory to html_static_path. They are copied after the
 # builtin static files, so a file named "default.css" will overwrite the

src/doc/en/developer/conf.py

@@ -13,11 +13,6 @@
 from sage_docbuild.conf import release
 from sage_docbuild.conf import *  # NOQA
 
-
-for tag in feature_tags():
-    tags.add(tag)
-
-
 # Add any paths that contain custom static files (such as style sheets),
 # relative to this directory to html_static_path. They are copied after the
 # builtin static files, so a file named "default.css" will overwrite the

src/doc/en/developer/packaging_sage_library.rst

@@ -495,17 +495,6 @@ requiring all of Sage to be present.
 mechanism mentioned above can also be used for this.
 
 
-Dependencies of the Sage documentation
---------------------------------------
-
-The documentation will not be modularized.
-
-However, some parts of the Sage reference manual may depend on functionality
-provided by optional packages. These portions of the reference manual
-should be conditionalized using the Sphinx directive ``.. ONLY::``,
-as explained in :ref:`section-documentation-conditional`.
-
-
 Version constraints of dependencies
 -----------------------------------
 

src/doc/en/developer/sage_manuals.rst

@@ -299,32 +299,6 @@ procedure is different:
 * Add your file to the index contained in
   :sage_root:`src/doc/en/reference/combinat/module_list.rst`.
 
-.. _section-documentation-conditional:
-
-Making portions of the reference manual conditional on optional features
-========================================================================
-
-For every dynamically detectable feature such as :class:`graphviz
-<~sage.features.graphviz.Graphviz>` or :class:`sage.symbolic
-<sage.features.sagemath.sage__symbolic>` (see :mod:`sage.features`),
-Sage defines a Sphinx tag that can be used with the `Sphinx
-directive ".. ONLY::"
-<https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#tags>`_.
-Because Sphinx tags have to use Python identifier syntax, Sage uses
-the format ``feature_``, followed by the feature name where dots are
-replaced by underscores. Hence, conditionalizing on the features of
-the previous examples would look as follows:
-
-.. CODE-BLOCK:: rest
-
-  .. ONLY:: feature_graphviz
-
-and:
-
-.. CODE-BLOCK:: rest
-
-  .. ONLY:: feature_sage_symbolic
-
 .. _section-building-manuals:
 
 Building the manuals