composer(deps-dev): bump ergebnis/test-util from 1.5.0 to 1.6.0

Bumps [ergebnis/test-util](https://github.com/ergebnis/test-util) from 1.5.0 to 1.6.0.
- [Release notes](https://github.com/ergebnis/test-util/releases)
- [Changelog](https://github.com/ergebnis/test-util/blob/main/CHANGELOG.md)
- [Commits](ergebnis/test-util@1.5.0...1.6.0)

---
updated-dependencies:
- dependency-name: ergebnis/test-util
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

composer.json

@@ -22,7 +22,7 @@
   "require-dev": {
     "ergebnis/composer-normalize": "^2.20.0",
     "ergebnis/license": "^1.2.0",
-    "ergebnis/test-util": "^1.5.0",
+    "ergebnis/test-util": "^1.6.0",
     "phpunit/phpunit": "^9.5.11",
     "psalm/plugin-phpunit": "~0.16.1",
     "symfony/filesystem": "^4.4.0 || ^5.0.0",