BREAKING(sidekiq.queues): rationalize queues. now have critical, default, low

Dear instances, make sure to update your sidekiq processes. Indead, we are adopting a new strategy for daemons that process our background
jobs.

Now their is only 3 queues on sidekiq (still, we keep archive/export on delayed job for now).

The big idea : allow any worker to deal with any queue (capacity mgmt) :
- critical: must be procesed now
- default: will be processed asap
- low: do it after everything else

FYI: we had 50% of our server capacity on reserved queues. Leading to
bottle neck processing (reserved queues/worker not processing other
queues). We HAD TO fix it. Sorry for the inconvenience

TBH, this is an idea of Colin Darie <colin@darie.eu>. I'm just pushing
it forward.

Co-Authored-By: Colin Darie <colin@darie.eu>

app/jobs/helpscout_create_conversation_job.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 class HelpscoutCreateConversationJob < ApplicationJob
-  queue_as :default
-
   class FileNotScannedYetError < StandardError
   end