Remove reference to old article

Author: Mark Pundsack

README.md

@@ -35,5 +35,4 @@ For more information about using Ruby on Heroku, see these Dev Center articles:
 
 - [Ruby on Heroku](https://devcenter.heroku.com/categories/ruby)
 - [Getting Started with Ruby on Heroku](https://devcenter.heroku.com/articles/getting-started-with-ruby)
-- [Getting Started with Rails 4.x on Heroku](https://devcenter.heroku.com/articles/getting-started-with-rails4)
 - [Heroku Ruby Support](https://devcenter.heroku.com/articles/ruby-support)