/**
* Deletes a specific instance.
*
* @param \Drupal\Core\Menu\MenuLinkInterface $instance
* The plugin instance to be deleted.
* @param bool $persist
* If TRUE, calls MenuLinkInterface::deleteLink() on the instance.
*
* @throws \Drupal\Component\Plugin\Exception\PluginException
* If the plugin instance does not support deletion.
*/