Set FlexiHelpFormatter release to 3.11

Rebase to force CI retest.

The "addres sanitizer" test is failing with a timeout, on
test_multiprocessing_fork.WithProcessesTestQueue(). It is not likely
that this branch contributed to that failure.

https://github.com/python/cpython/pull/22129/checks?check_run_id=3033564406

Author: davesteele

Doc/library/argparse.rst

@@ -490,7 +490,7 @@ single non-whitespace character followed by a "."::
      -h, --help  show this help message and exit
 
 
-.. versionadded:: 3.10
+.. versionadded:: 3.11
    :class:`FlexiHelpFormatter` class was added.
 
 :class:`ArgumentDefaultsHelpFormatter` automatically adds information about