mm/z3fold: remove obsolete comment for struct z3fold_pool

mm/z3fold: remove obsolete comment for struct z3fold_pool

Since commit e774a7bc7f0a ("mm: zswap: remove page reclaim logic from
z3fold"), zpool and zpool_ops have been removed, so also remove the
corresponding comments.

Link: https://lkml.kernel.org/r/20230814221142.486548-1-xiujianfeng@huaweicloud.com
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>