Use the new @-notation when referencing Twig templates (see #1382).

Description
-----------

Details available in [this PR](#1379).

> Update to the modern @-prefixed way of referencing templates.

Commits
-------

2e79392 Use the modern @-notation when referencing twig templates

src/Menu/BackendMenuRenderer.php

@@ -36,6 +36,6 @@ public function __construct(Environment $twig)
      */
     public function render(ItemInterface $tree, array $options = []): string
     {
-        return $this->twig->render('ContaoCoreBundle:Backend:be_menu.html.twig', ['tree' => $tree]);
+        return $this->twig->render('@ContaoCore/Backend/be_menu.html.twig', ['tree' => $tree]);
     }
 }

tests/Menu/BackendMenuRendererTest.php

@@ -52,7 +52,7 @@ public function testRendersTheBackendMenuTemplate(): void
         $this->templating
             ->expects($this->once())
             ->method('render')
-            ->with('ContaoCoreBundle:Backend:be_menu.html.twig', ['tree' => $tree])
+            ->with('@ContaoCore/Backend/be_menu.html.twig', ['tree' => $tree])
             ->willReturn('')
         ;