Bump phpunit/phpunit from 12.3.13 to 12.3.15

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 12.3.13 to 12.3.15.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/12.3.15/ChangeLog-12.3.md)
- [Commits](sebastianbergmann/phpunit@12.3.13...12.3.15)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-version: 12.3.15
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]