composer(deps-dev): update phpunit/phpunit requirement

Updates the requirements on [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) to permit the latest version.
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/10.3.1/ChangeLog-10.3.md)
- [Commits](sebastianbergmann/phpunit@10.2.7...10.3.1)

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

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

composer.json

@@ -37,7 +37,7 @@
     "phpstan/phpstan": "^1.10.26",
     "phpstan/phpstan-deprecation-rules": "^1.1.3",
     "phpstan/phpstan-phpunit": "^1.3.13",
-    "phpunit/phpunit": "^10.2.7",
+    "phpunit/phpunit": "^10.3.1",
     "rector/rector": "^0.17.10",
     "vimeo/psalm": "^5.14.1"
   },