tools(deps-dev): Update phpunit/phpunit requirement in /tools/phpunit (#456)

Updates the requirements on [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) to permit the latest version.
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/10.5.8/ChangeLog-10.5.md)
- [Commits](sebastianbergmann/phpunit@10.5.6...10.5.8)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

tools/phpunit/composer.json

@@ -3,7 +3,7 @@
     "type": "metapackage",
     "description": "phpunit",
     "require-dev": {
-        "phpunit/phpunit": "10.5.6",
+        "phpunit/phpunit": "10.5.8",
         "roave/security-advisories": "dev-latest"
     },
     "config": {