[oneTBB] task_handle related extensions

 - fixed typo

Signed-off-by: Anton Potapov <anton.potapov@intel.com>

Author: anton-potapov

source/elements/oneTBB/source/task_scheduler/task_arena/this_task_arena_ns.rst

@@ -1,5 +1,5 @@
-.. SPDX-FileCopyrightText: 2019-2021 Intel Corporation
-......................................................
+.. SPDX-FileCopyrightText: 2019-2020 Intel Corporation
+..
 .. SPDX-License-Identifier: CC-BY-4.0
 
 ===============
@@ -86,4 +86,4 @@ with the ``task_arena`` currently used by the calling thread.
     The behavior of this function is identical to the generic version (``template<typename F> void enqueue(F&& f)``), except the parameter type. 
 
     .. note:: 
-    ``h`` should not be empty to avoid an undefined behavior.
+        ``h`` should not be empty to avoid an undefined behavior.

source/elements/oneTBB/source/task_scheduler/task_group/task_handle.rst

@@ -39,6 +39,8 @@ An instance of ``task_handle`` type owns a deferred task object.
 Member Functions
 ----------------
 
+.. namespace:: tbb::task_handle
+
 .. cpp:function:: task_handle()
 
     Creates an empty ``task_handle`` object.