Remove text builds of documentation (#180)

This PR removes text builds of the documentation, which we do not currently use for anything. Contributes to rapidsai/build-planning#71.

Authors:
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - Ben Frederickson (https://github.com/benfred)
  - Corey J. Nolet (https://github.com/cjnolet)
  - Jake Awe (https://github.com/AyodeAwe)

URL: #180

Author: vyasr

ci/build_docs.sh

@@ -49,11 +49,9 @@ popd
 rapids-logger "Build Python docs"
 pushd docs
 sphinx-build -b dirhtml source _html
-sphinx-build -b text source _text
 mv ../rust/target/doc ./_html/_static/rust
-mkdir -p "${RAPIDS_DOCS_DIR}/cuvs/"{html,txt}
+mkdir -p "${RAPIDS_DOCS_DIR}/cuvs/"html
 mv _html/* "${RAPIDS_DOCS_DIR}/cuvs/html"
-mv _text/* "${RAPIDS_DOCS_DIR}/cuvs/txt"
 popd
 
 rapids-upload-docs