[3.14] gh-127502: Remove XML vulnerability table (GH-135294) (#136359)

gh-127502: Remove XML vulnerability table (GH-135294)

* Remove the table
* Replace warnings with notes

Latest releases of Python 3.9-3.15 include expat 2.7.1 which is not vulnerable.

expat 2.6.0 was released in February 2024.
(cherry picked from commit cb99d992774b67761441e122965ed056bac09241)

Co-authored-by: Victor Stinner <vstinner@python.org>