Update phpunit/phpunit requirement from ^11.3 to ^12.0 (#12)

Updates the requirements on [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) to permit the latest version.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/12.0.2/ChangeLog-12.0.md)
- [Commits](sebastianbergmann/phpunit@11.3.0...12.0.2)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-type: direct:development
...

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Author: dependabot[bot]

composer.json

@@ -21,7 +21,7 @@
         "friendsofphp/php-cs-fixer": "^3.64",
         "phpstan/phpstan": "^2.0.x-dev",
         "phpstan/phpstan-strict-rules": "^2.0.x-dev",
-        "phpunit/phpunit": "^11.3",
+        "phpunit/phpunit": "^12.0",
         "symplify/monorepo-builder": "^11.2"
     },
     "replace": {