[3.11] gh-108962: Skip test_tempfile.test_flags() if not supported (GH-108964) (#108968)

gh-108962: Skip test_tempfile.test_flags() if not supported (GH-108964)

Skip test_tempfile.test_flags() if chflags() fails with "OSError:
[Errno 45] Operation not supported" (ex: on FreeBSD 13).
(cherry picked from commit cd2ef21b076b494224985e266c5f5f8b37c66618)

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