Change Redis#exists calls to Redis#exists? to avoid deprecation warning (#14191)

app/workers/unpublish_announcement_worker.rb

@@ -8,7 +8,7 @@ class UnpublishAnnouncementWorker
     payload = Oj.dump(event: :'announcement.delete', payload: announcement_id.to_s)
 
     FeedManager.instance.with_active_accounts do |account|
-      redis.publish("timeline:#{account.id}", payload) if redis.exists("subscribed:timeline:#{account.id}")
+      redis.publish("timeline:#{account.id}", payload) if redis.exists?("subscribed:timeline:#{account.id}")
     end
   end
 end