mm/uffd: fix comment in handling pte markers

The comment is obsolete after f369b07c ("mm/uffd: reset write
protection when unregister with wp-mode", 2022-08-20).  Remove it.

Link: https://lkml.kernel.org/r/20230215205800.223549-1-peterx@redhat.com


Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>