`poll` plugin was publishing on `/polls/[topic_id]` every time a non-first post was created. I can't imagine this being needed. It regressed 3 years ago in https://github.com/discourse/discourse/pull/6359
* DEV: Remove spec that we no longer need.
As far as we know, the migration has been successful for a number of
years.
* FIX: Validate number of votes allowed per poll per user.