[3.13] gh-134109: Fix showing comments in pydoc output for argparse (GH-134110) (GH-134113)

Comments immediately preceding the object's source code are used
if the object has no docstring.
Comments that do not describe the object should be separated from
the following source code by an empty line.
(cherry picked from commit 71cf4dd622832848cace358a7f8444243afd2e83)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>