Resolve #3238915 "Refactor if feasible"

Closes #3238915

core/lib/Drupal/Core/Form/FormBuilderInterface.php

@@ -138,15 +138,11 @@ public function rebuildForm($form_id, FormStateInterface &$form_state, $old_form
    *
    * For example:
    * @code
-   * // register a new user
+   * // Set the administrator role to 'content_editor'.
+   * $values['user_admin_role'] = 'content_editor';
    * $form_state = new FormState();
-   * $values['name'] = 'some-user';
-   * $values['mail'] = 'someuser@example.com';
-   * $values['pass']['pass1'] = 'password';
-   * $values['pass']['pass2'] = 'password';
-   * $values['op'] = t('Create new account');
    * $form_state->setValues($values);
-   * \Drupal::formBuilder()->submitForm('user_register_form', $form_state);
+   * \Drupal::formBuilder()->submitForm(RoleSettingsForm::class, $form_state);
    * @endcode
    *
    * @param \Drupal\Core\Form\FormInterface|string $form_arg