Move the `project_update_repository_storage` off the realtime sidekiq queue

The realtime sidekiq queue is intended to be quick.

I'm not sure if we have any stated SLOs but we have tentatively started defining apdex thresolds for the various queues in https://gitlab.com/gitlab-com/runbooks/blob/master/rules/service_apdex.yml

However, the project_update_repository_storage job has a p99 duration peaking at 2.5 hours.

It definitely should not be on the realtime queue.

Moving it off will free queue workers up to handle incoming realtime jobs.

We should do this as a priority as this may be leading to queuing problems in sidekiq.

cc @ahmadsherif as EOC

ELK data: https://log.gitlab.net/goto/0df579431047ecc6e01cfe33c7dc33a7