run tests with symfony 7

Author: cebe

.github/workflows/php.yml

@@ -23,7 +23,7 @@ jobs:
         dependencies:
           - "lowest"
           - "highest"
-        symfony-yaml: ['^3.4', '^4', '^5', '^6']
+        symfony-yaml: ['^3.4', '^4', '^5', '^6', '^7']
         include:
           - os: "windows-latest"
             php: "8.0"