remove unused queues

- search_sync is staying around for now, because of how job uniqueness
is implemented
- seems like a good idea to also keep ‘default’ around even though no
worker/job uses it.  It is the default queue that sidekiq uses. So just
a smart move to keep it around?
- remove all other unused queues

:warning: Do not merge until https://github.com/assemblymade/coderwall/commit/d057062761b3007fa125983dd672a20b44da8507 has been deployed to Production and the old queues have emptied.