Temporary test 8.1 against dev version of Symfony

Author: alexander-schranz

.github/workflows/test-application.yaml

@@ -52,6 +52,7 @@ jobs:
                       database: mysql
                       dependency-versions: 'highest'
                       tools: 'composer:v2'
+                      composer-stability: 'dev'
                       env:
                           SYMFONY_DEPRECATIONS_HELPER: weak
                           DATABASE_URL: mysql://root:root@127.0.0.1/sulu_form_test?serverVersion=5.7