Update dependency phpunit/phpunit to v12 (#46)

Co-authored-by: descope[bot] <107609351+descope[bot]@users.noreply.github.com>

Author: descope[bot]

composer.json

@@ -21,7 +21,7 @@
     "vlucas/phpdotenv": "^5.6.1"
   },
   "require-dev": {
-    "phpunit/phpunit": "^11.0",
+    "phpunit/phpunit": "^12.0",
     "squizlabs/php_codesniffer": "*"
   },
   "autoload": {