build: change php version

Closes #19

Author: josantonius

composer.json

@@ -27,7 +27,7 @@
     },
     "require-dev": {
         "phpmd/phpmd": "^2.6",
-        "phpunit/phpunit": "^9.0",
+        "phpunit/phpunit": "^9.5",
         "squizlabs/php_codesniffer": "^3.7"
     },
     "minimum-stability": "stable",