Maestro updates PHPUnit

Author: dantleech

composer.json

@@ -14,7 +14,7 @@
         "webmozart/path-util": "^2.3"
     },
     "require-dev": {
-        "phpunit/phpunit": "~7.0",
+        "phpunit/phpunit": "^9.0",
         "symfony/filesystem": "^3.2",
         "friendsofphp/php-cs-fixer": "~2.15.0",
         "phpstan/phpstan": "~0.12.0"
@@ -41,4 +41,4 @@
             "vendor/bin/phpunit"
         ]
     }
-}
+}