Update phpunit/phpunit requirement from ^9.6 to ^10.4

Updates the requirements on [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) to permit the latest version.
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/10.4.1/ChangeLog-10.4.md)
- [Commits](sebastianbergmann/phpunit@9.6.0...10.4.1)

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

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

composer.json

@@ -31,7 +31,7 @@
         "phpstan/phpstan": "^1.8.11",
         "squizlabs/php_codesniffer": "3.*",
         "oxid-esales/oxideshop-ce": "dev-b-7.1.x",
-        "phpunit/phpunit": "^9.6"
+        "phpunit/phpunit": "^10.4"
     },
     "autoload":    {
         "psr-4": {