Fix normalized_reflections :nodoc: typo

It was meant to be private API.

Author: byroot

activerecord/lib/active_record/reflection.rb

@@ -79,7 +79,7 @@ def reflections
         normalized_reflections.stringify_keys
       end
 
-      def normalized_reflections # :nodoc
+      def normalized_reflections # :nodoc:
         @__reflections ||= begin
           ref = {}