Bump phpunit/phpunit from 11.5.25 to 11.5.50 in /tests

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 11.5.25 to 11.5.50.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/11.5.50/ChangeLog-11.5.md)
- [Commits](https://github.com/sebastianbergmann/phpunit/compare/11.5.25...11.5.50)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-version: 11.5.50
  dependency-type: direct:development
...

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