Fix ruby warnings about deprecated keyword arguments.

app/models/post_event.rb

@@ -71,7 +71,7 @@ class PostEvent
   end
 
   # XXX can't use hidden_attributes because we don't inherit from ApplicationRecord.
-  def serializable_hash(**options)
+  def serializable_hash(options = {})
     hash = super
     hash = hash.except(:creator_id) unless is_creator_visible?
     hash

app/models/saved_search.rb

@@ -150,7 +150,7 @@ class SavedSearch < ApplicationRecord
     end
 
     def normalized_query
-      PostQueryBuilder.new(query).normalized_query.to_s
+      @normalized_query ||= PostQueryBuilder.new(query).normalized_query.to_s
     end
 
     def rewrite_query(old_name, new_name)