gh-90473: Make chmod a dummy on WASI, skip chmod tests (GH-93534) (GH-93550)

WASI does not have the ``chmod(2)`` syscall yet.
(cherry picked from commit 22fed605e096eb74f3aa33f6d25aee76fdc2a3fa)

Co-authored-by: Christian Heimes <christian@python.org>