Merge topic 'FindThreads-revert-libc-pthread-flag' into release-3.23

c6da90bd39 FindThreads: Revert "Honor THREADS_PREFER_PTHREAD_FLAG when ... in libc"

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !7025