Bump the composer-dependencies group with 1 update

Bumps the composer-dependencies group with 1 update: [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit).


Updates `phpunit/phpunit` from 9.6.15 to 9.6.16
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/9.6.16/ChangeLog-9.6.md)
- [Commits](sebastianbergmann/phpunit@9.6.15...9.6.16)

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

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