Enable RSpec zero monkey patching mode

The plan for RSpec 4.0 is to disable monkey patching.

See https://github.com/rspec/rspec-core/blob/main/features/configuration/zero_monkey_patching_mode.feature for details.

spec/controllers/application_controller_spec.rb

@@ -28,7 +28,7 @@
 
 require 'spec_helper'
 
-describe ApplicationController do
+RSpec.describe ApplicationController do
   let(:user) { create(:user, lastname: "Crazy! Name with \r\n Newline") }
 
   # Fake controller to test calling an action