mm: memcontrol: remove stale page_cgroup_lock comment

There is no cgroup-specific page lock anymore.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -2467,10 +2467,6 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
 	int isolated;
 
 	VM_BUG_ON_PAGE(pc->mem_cgroup, page);
-	/*
-	 * we don't need page_cgroup_lock about tail pages, becase they are not
-	 * accessed by any other context at this point.
-	 */
 
 	/*
 	 * In some cases, SwapCache and FUSE(splice_buf->radixtree), the page