after_generator config should only be for development

I think it makes more sense to have this code only present in development.

README.md

@@ -66,17 +66,15 @@ end
 ## Rails configuration tip
 
 If you are using Rails 6.1 or newer, add the following `config.generators.after_generate` setting to
-your config/application.rb to apply RuboCop autocorrection to code generated by `bin/rails g`.
+your `config/environments/development.rb` to apply RuboCop autocorrection to code generated by `bin/rails g`.
 
 ```ruby
-# config/application.rb
-module YourCoolApp
-  class Application < Rails::Application
-    config.generators.after_generate do |files|
-      parsable_files = files.filter { |file| file.end_with?('.rb') }
-      unless parsable_files.empty?
-        system("bundle exec rubocop -A --fail-level=E #{parsable_files.shelljoin}", exception: true)
-      end
+# config/environments/development.rb
+Rails.application.configure do
+  config.generators.after_generate do |files|
+    parsable_files = files.filter { |file| file.end_with?('.rb') }
+    unless parsable_files.empty?
+      system("bundle exec rubocop -A --fail-level=E #{parsable_files.shelljoin}", exception: true)
     end
   end
 end