Import Galera 26.4.23 minor maintenance release

Similar to MRs labeled new-upstream-version, this Merge Request contains the import of a new upstream version.

Do not review merge commits or upstream commits, but focus on the ones that are made only on the proposed debian/latest branch update in this MR:

git log --first-parent --reverse --format='format:* %C(yellow)%h%C(reset) %s' debian/latest...

• f8cb99c4 Update upstream source from tag 'upstream/26.4.23'
• 6795b91d Update changelog and refresh patches after 26.4.23 import

Changelog:

galera-4 (26.4.23-1) UNRELEASED; urgency=medium

  * New upstream release 26.4.23. Includes multiple bug fixes, see
    https://github.com/codership/documentation/blob/master/release-notes/release-notes-galera-26.4.23.txt
  * Drop patch to fix garbd's -w/WORK_DIR parameter that is now applied upstream

 -- Otto Kekäläinen <otto@debian.org>  Tue, 12 Aug 2025 13:00:40 -0700

I am not aware of any additional Debian tracked bugs at https://bugs.debian.org/cgi-bin/pkgreport.cgi?repeatmerged=no&src=mariadb that would be fixed by this version.

Note also test builds on multiple architectures at https://launchpad.net/~mysql-ubuntu/+archive/ubuntu/mariadb/+builds?build_text=&build_state=all