feat: upgrade phpunit to 12.5

tests/Controller/Groups/Booking/Step2ControllerTest.php

@@ -38,7 +38,7 @@ class Step2ControllerTest extends TestCase
         $sessionManager = new AccommodationSessionManager();
         $sessionManager->save($request, $dto);
 
-        $form = $this->createMock(FormInterface::class);
+        $form = $this->createStub(FormInterface::class);
         $form
             ->method('handleRequest')
             ->willReturnCallback(function () use ($dto, $form): FormInterface {