composer(deps-dev): update phpunit/phpunit requirement

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/master/ChangeLog-9.5.md)
- [Commits](sebastianbergmann/phpunit@9.5.14...9.5.16)

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

Signed-off-by: dependabot[bot] <support@github.com>

composer.json

@@ -26,7 +26,7 @@
     "require-dev": {
         "ext-ds": "*",
         "phpstan/phpstan": "^1.4",
-        "phpunit/phpunit": "^9.5.14",
+        "phpunit/phpunit": "^9.5.16",
         "roave/security-advisories": "dev-master",
         "squizlabs/php_codesniffer": "^3.6.2",
         "symfony/serializer": "^5.4"