Bump PHPUnit

Author: JaZo

composer.json

@@ -17,7 +17,7 @@
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^3.0",
         "guzzlehttp/guzzle": "^7.3",
-        "phpunit/phpunit": "^8.0|^9.0",
+        "phpunit/phpunit": "^9.5",
         "php-http/mock-client": "^1.2"
     },
     "suggest": {