Remove Gitlab::Redis::DuplicateJobs
This removes Gitlab::Redis::DuplicateJobs. We thought we needed this new functional Redis shard to prevent saturation of redis-sidekiq on GitLab.com but we avoided that problem through other means.
The Gitlab::Redis::DuplicateJobs Redis instance was hidden behind feature flags that were off by default; nobody should be using it. Even if they were, job deduplication will keep working correctly because of !109098 (merged).
Edited by Jacob Vosmaer