Bump PHPUnit

Author: JaZo

composer.json

@@ -32,7 +32,7 @@
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^3.0",
         "guzzlehttp/guzzle": "^7.3",
-        "phpunit/phpunit": "^9.0"
+        "phpunit/phpunit": "^9.5"
     },
     "provide": {
         "php-http/async-client-implementation": "1.0",