build(deps-dev): bump phpunit/phpunit from 12.1.5 to 12.1.6

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 12.1.5 to 12.1.6.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/12.1.6/ChangeLog-12.1.md)
- [Commits](sebastianbergmann/phpunit@12.1.5...12.1.6)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-version: 12.1.6
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]