Merge pull request rails#25716 from willnet/remove-rails-4

[ci skip] Remove reference to Rails 4 in the initialization guide.

Author: prathamesh-sonpatki

guides/source/initialization.md

@@ -16,7 +16,7 @@ After reading this guide, you will know:
 --------------------------------------------------------------------------------
 
 This guide goes through every method call that is
-required to boot up the Ruby on Rails stack for a default Rails 4
+required to boot up the Ruby on Rails stack for a default Rails
 application, explaining each part in detail along the way. For this
 guide, we will be focusing on what happens when you execute `rails server`
 to boot your app.