Update phpunit/phpunit requirement from ^9.1 to ^9.1 || ^11.0

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/11.2.6/ChangeLog-11.2.md)
- [Commits](sebastianbergmann/phpunit@9.1.0...11.2.6)

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

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

composer.json

@@ -15,7 +15,7 @@
     },
     "license": "GPL-3.0-or-later",
     "require-dev": {
-        "phpunit/phpunit": "^9.1",
+        "phpunit/phpunit": "^9.1 || ^11.0",
         "http-interop/http-factory-guzzle": "^1.0",
         "infection/infection": "^0.26",
         "phpstan/phpstan": "^1.0.0",