Remove check for rails-controller-testing gem

The `rails-controller-testing` gem provided helper methods for controller tests up to Rails 4.2. This condition was used to support testing with both Rails 4.2 and Rails 5+. Since we no longer test with Rails versions below 5, the condition is no longer necessary.

ref: #21

Author: willnet

spec/spec_helper.rb

@@ -35,13 +35,7 @@ class TestMailer < ActionMailer::Base; end
   config.include ::Sorcery::TestHelpers::Internal
   config.include ::Sorcery::TestHelpers::Internal::Rails
 
-  if begin
-       Module.const_defined?('::Rails::Controller::Testing')
-     rescue StandardError
-       false
-     end
-    config.include ::Rails::Controller::Testing::TestProcess, type: :controller
-    config.include ::Rails::Controller::Testing::TemplateAssertions, type: :controller
-    config.include ::Rails::Controller::Testing::Integration, type: :controller
-  end
+  config.include ::Rails::Controller::Testing::TestProcess, type: :controller
+  config.include ::Rails::Controller::Testing::TemplateAssertions, type: :controller
+  config.include ::Rails::Controller::Testing::Integration, type: :controller
 end