Update phpunit/phpunit requirement from ^9.0 to ^11.2

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/11.2.6/ChangeLog-11.2.md)
- [Commits](sebastianbergmann/phpunit@9.0.0...11.2.6)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

composer.json

@@ -25,7 +25,7 @@
         "enlightn/security-checker": "^1.10 || ^2.0",
         "guzzlehttp/guzzle": "^6.5.8 || ^7.4.5",
         "guzzlehttp/psr7": "^1.9.1 || ^2.4.5",
-        "phpunit/phpunit": "^9.0",
+        "phpunit/phpunit": "^11.2",
         "symfony/mailer": "^6.0 || ^7.0"
     },
     "config": {