mm/compaction: correct comment to complete migration failure

Commit cfccd2e6 ("mm, compaction: finish pageblocks on complete
migration failure") convert cc->order aligned check to page block order
aligned check.  Correct comment relevant with it.

Link: https://lkml.kernel.org/r/20230804110454.2935878-7-shikemeng@huaweicloud.com


Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>