Bump PHPUnit Version

Author: mcordingley

composer.json

@@ -16,7 +16,7 @@
         "php": "^8.0.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^8.0.0"
+        "phpunit/phpunit": "^9.5.0"
     },
     "autoload": {
         "psr-4": {