[TwigBridge] Fix for GitHub ticket 50789

Change the return type of AppVariable.php getSession from 'Session' to 'SessionInterface', to be in line with the return type of getSession in http-foundation/Request.php

src/Symfony/Bridge/Twig/AppVariable.php

@@ -13,7 +13,7 @@
 
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\RequestStack;
-use Symfony\Component\HttpFoundation\Session\Session;
+use Symfony\Component\HttpFoundation\Session\SessionInterface;
 use Symfony\Component\Security\Core\Authentication\Token\Storage\TokenStorageInterface;
 use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
 use Symfony\Component\Security\Core\User\UserInterface;
@@ -93,7 +93,7 @@ public function getRequest(): ?Request
     /**
      * Returns the current session.
      */
-    public function getSession(): ?Session
+    public function getSession(): ?SessionInterface
     {
         if (!isset($this->requestStack)) {
             throw new \RuntimeException('The "app.session" variable is not available.');