Update phpunit/phpunit requirement from ^8.5.14 to ^8.5.14 || ^9.0.0

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/master/ChangeLog-9.5.md)
- [Commits](sebastianbergmann/phpunit@8.5.14...9.5.3)

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

composer.json

@@ -26,7 +26,7 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "^8.5.14",
+        "phpunit/phpunit": "^8.5.14 || ^9.0.0",
         "phpstan/phpstan": "0.12.81",
         "diablomedia/zendframework1-view-helper-layout": "^1.0",
         "friendsofphp/php-cs-fixer": "2.18.3",