ceph: rely on vfs for setgid stripping

Now that we finished moving setgid stripping for regular files in setgid
directories into the vfs, individual filesystem don't need to manually
strip the setgid bit anymore. Drop the now unneeded code from ceph.

Link: https://lore.kernel.org/r/1657779088-2242-4-git-send-email-xuyang2018.jy@fujitsu.com
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Christian Brauner <(Microsoft)&lt;brauner@kernel.org>
Reviewed-and-Tested-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>