composer(deps-dev): bump phpunit/phpunit from 9.5.20 to 9.5.21

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 9.5.20 to 9.5.21.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/main/ChangeLog-9.5.md)
- [Commits](sebastianbergmann/phpunit@9.5.20...9.5.21)

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

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

Author: dependabot[bot]

composer.json

@@ -23,7 +23,7 @@
     "ergebnis/composer-normalize": "^2.28.0",
     "ergebnis/license": "^1.2.0",
     "fakerphp/faker": "^1.19.0",
-    "phpunit/phpunit": "^9.5.20",
+    "phpunit/phpunit": "^9.5.21",
     "psalm/plugin-phpunit": "~0.17.0",
     "symfony/filesystem": "^4.4.0 || ^5.0.0",
     "vimeo/psalm": "^4.23"