Improve our Sidekiq testing best practices

What does this MR do?

I realize that we advertise the usage of perform_enqueued_jobs even though it does nothing since our worker classes don't inherit from ApplicationJob / ActiveJob::Base.

This MR hopefully makes it clearer.

Does this MR meet the acceptance criteria?

Conformity

• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content