gh-93353: Fix importlib.resources._tempfile() finalizer (GH-93377)

Fix the importlib.resources.as_file() context manager to remove the
temporary file if destroyed late during Python finalization: keep a
local reference to the os.remove() function. Patch by Victor Stinner.
(cherry picked from commit 443ca731d6b1267fe2f92985e0490460c95e44a8)

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