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

app/lib/activitypub/activity.rb

@@ -132,7 +132,7 @@ class ActivityPub::Activity
   end
 
   def delete_arrived_first?(uri)
-    redis.exists("delete_upon_arrival:#{@account.id}:#{uri}")
+    redis.exists?("delete_upon_arrival:#{@account.id}:#{uri}")
   end
 
   def delete_later!(uri)

app/lib/activitypub/activity/move.rb

@@ -33,7 +33,7 @@ class ActivityPub::Activity::Move < ActivityPub::Activity
   end
 
   def processed?
-    redis.exists("move_in_progress:#{@account.id}")
+    redis.exists?("move_in_progress:#{@account.id}")
   end
 
   def mark_as_processing!