Update phpunit/phpunit requirement from ^10.2.4 to ^10.2.6 (#131)

Updates the requirements on [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) to permit the latest version.
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/10.2.6/ChangeLog-10.2.md)
- [Commits](sebastianbergmann/phpunit@10.2.4...10.2.6)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

composer.json

@@ -18,7 +18,7 @@
   },
   "require-dev": {
     "doctrine/coding-standard": "^12.0",
-    "phpunit/phpunit": "^10.2.4",
+    "phpunit/phpunit": "^10.2.6",
     "psalm/plugin-phpunit": "^0.18.4",
     "vimeo/psalm": "^5.13"
   },