Remove warning of circular require

This file was using mime_types before load the Mime::Type class.
When trying to register first Mime::Type it load mime_type that loads
mime_types in the end.

Requiring mime_type ensure that we have the class definition and the
mime types

actionpack/lib/action_controller/metal/params_wrapper.rb

@@ -2,7 +2,7 @@
 require 'active_support/core_ext/hash/except'
 require 'active_support/core_ext/module/anonymous'
 require 'active_support/core_ext/struct'
-require 'action_dispatch/http/mime_types'
+require 'action_dispatch/http/mime_type'
 
 module ActionController
   # Wraps the parameters hash into a nested hash. This will allow clients to submit