PERF: no need to nest a transaction when featuring topics

adding featured topics is already in a transaction, no need to nest

app/models/category_featured_topic.rb

@@ -4,14 +4,12 @@ class CategoryFeaturedTopic < ActiveRecord::Base
 
   # Populates the category featured topics
   def self.feature_topics
-    transaction do
-      current = {}
-      CategoryFeaturedTopic.select(:topic_id, :category_id).order(:rank).each do |f|
-        (current[f.category_id] ||= []) << f.topic_id
-      end
-      Category.select(:id, :topic_id).find_each do |c|
-        CategoryFeaturedTopic.feature_topics_for(c, current[c.id] || [])
-      end
+    current = {}
+    CategoryFeaturedTopic.select(:topic_id, :category_id).order(:rank).each do |f|
+      (current[f.category_id] ||= []) << f.topic_id
+    end
+    Category.select(:id, :topic_id).find_each do |c|
+      CategoryFeaturedTopic.feature_topics_for(c, current[c.id] || [])
     end
   end