Bump phpunit/phpunit from 9.5.20 to 9.5.28

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 9.5.20 to 9.5.28.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/9.5.28/ChangeLog-9.5.md)
- [Commits](sebastianbergmann/phpunit@9.5.20...9.5.28)

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

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

composer.json

@@ -15,7 +15,7 @@
         "squizlabs/php_codesniffer": "^3.6.2"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.5.20"
+        "phpunit/phpunit": "^9.5.28"
     },
     "autoload": {
         "psr-4": {