feat(cops): clean rubocop run

1. ignoring one file because it's an intentional vuln
2. made a few small semantic changes, but verified that they're equivalent.

app/controllers/tutorials_controller.rb

@@ -3,8 +3,5 @@ class TutorialsController < ApplicationController
   skip_before_action :has_info
   skip_before_action :authenticated
 
-  def credentials
-    render layout: false
-  end
-
+  layout false, only: [:credentials]
 end