remove `per_form_csrf_tokens` initializer from Rails API

Because the form is not in the Rails API,
`per_form_csrf_tokens` initializer I think unnecessary.

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -327,6 +327,7 @@ def delete_non_api_initializers_if_api_option
           remove_file 'config/initializers/session_store.rb'
           remove_file 'config/initializers/cookies_serializer.rb'
           remove_file 'config/initializers/request_forgery_protection.rb'
+          remove_file 'config/initializers/per_form_csrf_tokens.rb'
         end
       end
 

railties/test/generators/api_app_generator_test.rb

@@ -89,6 +89,7 @@ def skipped_files
        config/initializers/cookies_serializer.rb
        config/initializers/session_store.rb
        config/initializers/request_forgery_protection.rb
+       config/initializers/per_form_csrf_tokens.rb
        lib/assets
        vendor/assets
        test/helpers