FEATURE: correct muted category implementation

- Don't change tracking state on muted categories
- Exclude muted sub categories from parent

lib/topic_creator.rb

@@ -19,17 +19,12 @@ class TopicCreator
     process_private_message
     save_topic
     watch_topic
-    auto_mute_topic
 
     @topic
   end
 
   private
 
-  def auto_mute_topic
-    CategoryUser.auto_mute_new_topic(@topic)
-  end
-
   def watch_topic
     unless @opts[:auto_track] == false
       @topic.notifier.watch_topic!(@topic.user_id)