feat: allow PHPUnit 9

Author: Chris8934

composer.json

@@ -25,7 +25,7 @@
         "ext-json": "*",
         "ext-libxml": "*",
         "composer-runtime-api": "^2.0",
-        "phpunit/phpunit": "^10.0|^11.0|^12.0",
+        "phpunit/phpunit": "^9.6|^10.0|^11.0|^12.0",
         "symfony/property-access": "^5.2|^6.2|^7.0|^8.0",
         "symfony/serializer": "^5.2|^6.2|^7.0|^8.0",
         "symfony/yaml": "^5.2|^6.2|^7.0|^8.0"