Fix require usage for active_support

As described in rails/rails#14664 use require 'active_support' before core_ext

lib/docs.rb

@@ -1,6 +1,7 @@
 require 'bundler/setup'
 Bundler.require :docs
 
+require 'active_support'
 require 'active_support/core_ext'
 I18n.enforce_available_locales = true