Restore Contao 4.13 compatibility

The method isBackendScope() was introduced in Contao 5 only. Use Scope matcher directly

src/ContentElement/ContentNavigationElement.php

@@ -41,7 +41,7 @@ public function __construct(
     /** @SuppressWarnings(PHPMD.Superglobals) */
     protected function getResponse(Template $template, ContentModel $model, Request $request): Response
     {
-        if ($this->isBackendScope($request)) {
+        if (! $this->container->get('contao.routing.scope_matcher')->isBackendRequest($request)) {
             return $this->getBackendView($model, $template);
         }