Fix single Redis connection being used across all threads (#18135)

* Fix single Redis connection being used across all Sidekiq threads

* Fix tests

app/workers/merge_worker.rb

@@ -2,12 +2,13 @@
 
 class MergeWorker
   include Sidekiq::Worker
+  include Redisable
 
   def perform(from_account_id, into_account_id)
     FeedManager.instance.merge_into_home(Account.find(from_account_id), Account.find(into_account_id))
   rescue ActiveRecord::RecordNotFound
     true
   ensure
-    Redis.current.del("account:#{into_account_id}:regeneration")
+    redis.del("account:#{into_account_id}:regeneration")
   end
 end