Allow PHPUnit 9.6 again

Author: fulopattila122

composer.json

@@ -18,7 +18,7 @@
         "ext-ctype": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "^10.0|^11.0"
+        "phpunit/phpunit": "^9.6|^10.0|^11.0"
     },
     "autoload": {
         "psr-4": { "Konekt\\Enum\\": "src/" }