Update phpunit/phpunit requirement from ^9.5 to ^11.2

Updates the requirements on [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) to permit the latest version.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/11.2.7/ChangeLog-11.2.md)
- [Commits](sebastianbergmann/phpunit@9.5.0...11.2.7)

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

Signed-off-by: dependabot[bot] <[email protected]>

composer.json

@@ -20,7 +20,7 @@
         "psr-4": { "League\\ISO3166\\": "src" }
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.5"
+        "phpunit/phpunit": "^11.2"
     },
     "autoload-dev": {
         "psr-4": { "League\\ISO3166\\": "tests" }