Restore PHPUnit version specification to ^9.5 || ^10.0 || ^11.0 || ^12.0

Co-authored-by: anderly <[email protected]>

Author: Copilot

composer.json

@@ -26,7 +26,7 @@
     },
     "require-dev": {
         "guzzlehttp/guzzle": "^7.0",
-        "phpunit/phpunit": "*",
+        "phpunit/phpunit": "^9.5 || ^10.0 || ^11.0 || ^12.0",
         "phpstan/phpstan": "^2.1"
     },
     "suggest": {