[Cleanup] use message_filter() over check() param (#2180)

Cleanup's helper method to collect messages to delete was incorrectly filtering by check rather than message_filter, causing delete_after to be ignored.

redbot/cogs/cleanup/cleanup.py

@@ -94,7 +94,7 @@ class Cleanup(commands.Cog):
         ):
             if message.created_at < two_weeks_ago:
                 break
-            if check(message):
+            if message_filter(message):
                 collected.append(message)
                 if number and number <= len(collected):
                     break