Bump phpunit/phpunit from 8.5.31 to 9.5.26 (#27)

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 8.5.31 to 9.5.26.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/main/ChangeLog-8.5.md)
- [Commits](sebastianbergmann/phpunit@8.5.31...9.5.26)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

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

Author: dependabot[bot]

composer.json

@@ -8,7 +8,7 @@
         "doctrine/collections": "^1.5"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.3 || ^8.0",
+        "phpunit/phpunit": "^7.3 || ^8.0 || ^9.0",
         "squizlabs/php_codesniffer": "^3.3"
     },
     "minimum-stability": "dev",