Bump phpunit/phpunit from 11.5.3 to 11.5.6

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 11.5.3 to 11.5.6.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/11.5.6/ChangeLog-11.5.md)
- [Commits](sebastianbergmann/phpunit@11.5.3...11.5.6)

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

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

Author: dependabot[bot]