AS::Callbacks.__run_keyed_callback: remove unused cache

activesupport/lib/active_support/callbacks.rb

@@ -394,16 +394,12 @@ module ActiveSupport
       #
       def __run_keyed_callback(key, kind, object, &blk) #:nodoc:
         name = "_run__#{self.name.hash.abs}__#{kind}__#{key.hash.abs}__callbacks"
-        unless respond_to?(name)
-          @_keyed_callbacks ||= {}
-          @_keyed_callbacks[name] ||= begin
+        unless object.respond_to?(name)
           str = send("_#{kind}_callbacks").compile(name, object)
           class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
             def #{name}() #{str} end
             protected :#{name}
           RUBY_EVAL
-            true
-          end
         end
         object.send(name, &blk)
       end