There aren't any bots that auto-delete articles. There are a handful of bots with administrator privileges, but they can only do things that humans have specified, with significant delay. For example, there was one (no longer active) that deleted empty categories that had been flagged by a human for deletion as empty, and not challenged for N days. There was also one (haven't followed up on whether it's still active) that deleted images that were tagged as copyright violations for more than N days.