Revert "Fix: フィルター使用中にエラーが出る場合がある問題の暫定対応 (#395)" (#405)

This reverts commit a6df29a925.

app/serializers/rest/filter_serializer.rb

@@ -12,14 +12,4 @@ class REST::FilterSerializer < ActiveModel::Serializer
   def rules_requested?
     instance_options[:rules_requested]
   end
-
-  # FIRST AID
-  # After the upstream is corrected, delete the following.
-  def title
-    object.phrase
-  end
-
-  def filter_action
-    object.action
-  end
 end