Update phpunit/phpunit requirement from ^12.5 to ^12.5 || ^13.0

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/13.1.7/ChangeLog-13.1.md)
- [Commits](sebastianbergmann/phpunit@12.5.0...13.1.7)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-version: 13.1.7
  dependency-type: direct:development
...

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

Author: dependabot[bot]

composer.json

@@ -33,7 +33,7 @@
     "require-dev": {
         "nyholm/psr7": "^1.8",
         "phpstan/phpstan": "^2.0",
-        "phpunit/phpunit": "^12.5",
+        "phpunit/phpunit": "^12.5 || ^13.0",
         "respect/coding-standard": "^5.0",
         "squizlabs/php_codesniffer": "^4.0"
     },