Optimize bridge_get_account_posts_by_replies by moving "ORDER BY ar.id DESC"...

Optimize bridge_get_account_posts_by_replies by moving "ORDER BY ar.id DESC" out of inner query so that optimizer doesn't think it should do a sequential scan of hive_posts (the LIMIT + ORDER BY seems to have led it astray). Previous code was too slow when the author didn't have any posts that could be replied to.