mm/compaction: remove unnecessary "else continue" at end of loop in isolate_freepages_block

There is no behavior change to remove "else continue" code at end of scan
loop.  Just remove it to make code cleaner.

Link: https://lkml.kernel.org/r/20230803094901.2915942-5-shikemeng@huaweicloud.com


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