Require PHPUnit 12 for demo application

Author: OskarStark

demo/composer.json

@@ -48,7 +48,7 @@
         "php-cs-fixer/shim": "^3.90",
         "phpstan/phpstan": "^2.1.32",
         "phpstan/phpstan-strict-rules": "^2.0.7",
-        "phpunit/phpunit": "^11.5.44",
+        "phpunit/phpunit": "^12.1",
         "symfony/browser-kit": "^7.3.6",
         "symfony/debug-bundle": "^7.3.5",
         "symfony/stopwatch": "^7.3",