Enable UniqueRetryJobMiddleware even when called from sidekiq worker (#4836)

config/initializers/sidekiq.rb

@@ -9,6 +9,9 @@ end
 
 Sidekiq.configure_server do |config|
   config.redis = redis_params
+  config.client_middleware do |chain|
+    chain.add Mastodon::UniqueRetryJobMiddleware
+  end
 end
 
 Sidekiq.configure_client do |config|