build(deps-dev): bump phpunit/phpunit in /tools/phpunit

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 11.5.55 to 13.1.0.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/13.1.0/ChangeLog-13.1.md)
- [Commits](sebastianbergmann/phpunit@11.5.55...13.1.0)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-version: 13.1.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

tools/phpunit/composer.json

@@ -3,7 +3,7 @@
   "description": "Flow PHP ETL - Tools",
   "require-dev": {
     "php": "~8.3.0 || ~8.4.0 || ~8.5.0",
-    "phpunit/phpunit": "^11"
+    "phpunit/phpunit": "^13"
   },
   "config": {
     "allow-plugins": false