Require newer phpunit patch version in devDependencies

Make it harder to accidentally install a version that doesn't support
the latest php releases during development.

Author: TysonAndre

composer.json

@@ -6,7 +6,7 @@
         "php": ">=7.2"
     },
     "require-dev": {
-        "phpunit/phpunit": "^8.5.15"
+        "phpunit/phpunit": "^8.5.30"
     },
     "license": "MIT",
     "authors": [