Add autoload hook for AbstractController::ActionNotFound

The error can be reproduced with

    require "bundler/setup"
    require "action_controller"

    AbstractController::ActionNotFound

actionpack/lib/abstract_controller.rb

@@ -7,6 +7,7 @@
 module AbstractController
   extend ActiveSupport::Autoload
 
+  autoload :ActionNotFound, "abstract_controller/base"
   autoload :Base
   autoload :Caching
   autoload :Callbacks