Merge pull request #13500 from arunagw/remove-unused-require

rbconfig is not used in these files remove unused requires

railties/lib/rails/engine.rb

@@ -2,7 +2,6 @@
 require 'rails/engine/railties'
 require 'active_support/core_ext/module/delegation'
 require 'pathname'
-require 'rbconfig'
 
 module Rails
   # <tt>Rails::Engine</tt> allows you to wrap a specific Rails application or subset of

railties/lib/rails/test_unit/testing.rake

-require 'rbconfig'
 require 'rake/testtask'
 require 'rails/test_unit/sub_test_task'