[3.13] gh-105376: Restore deprecated logging warn() method (GH-122775) (#122856)

gh-105376: Restore deprecated logging warn() method (GH-122775)

This reverts commit dcc028d92428bd57358a5028ada2a53fc79fc365 and
commit 6c54e5d72166d012b52155cbf13af9e533290e06.

Keep the deprecated logging warn() method in Python 3.13.

(cherry picked from commit d3239976a8e66ae3e2f4314a6889d79cdc9a9625)

Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>