Bump phpunit/phpunit from 11.5.50 to 12.5.22 in /tests

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 11.5.50 to 12.5.22.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/12.5.22/ChangeLog-12.5.md)
- [Commits](https://github.com/sebastianbergmann/phpunit/compare/11.5.50...12.5.22)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-version: 12.5.22
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

tests/composer.json

@@ -1,7 +1,7 @@
 {
     "name": "una.io/una-tests",
     "require-dev": {
-        "phpunit/phpunit": "11.*",
+        "phpunit/phpunit": "12.*",
         "phpmd/phpmd": "@stable"
     }
 }