build(deps-dev): bump phpunit/phpunit from 11.2.6 to 11.2.8

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 11.2.6 to 11.2.8.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/11.2.8/ChangeLog-11.2.md)
- [Commits](sebastianbergmann/phpunit@11.2.6...11.2.8)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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