[1.5] Remove migration worker files and add migration with sidekiq_remove_jobs

As the next step in #409873 (closed) for Step 1 - removing the migration workers, in this task we would like to remove the worker files.

From the guideline:

1. Delete the worker class file and follow the guidance in our Sidekiq queues documentation around running Rake tasks to regenerate/update related files.
2. Add a migration (not a post-deployment migration) that uses sidekiq_remove_jobs