composer(deps-dev): bump phpunit/phpunit from 8.5.15 to 9.5.4

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 8.5.15 to 9.5.4.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/master/ChangeLog-8.5.md)
- [Commits](sebastianbergmann/phpunit@8.5.15...9.5.4)

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

composer.json

@@ -25,7 +25,7 @@
     "phpstan/phpstan-deprecation-rules": "~0.12.6",
     "phpstan/phpstan-phpunit": "~0.12.18",
     "phpstan/phpstan-strict-rules": "~0.12.9",
-    "phpunit/phpunit": "^8.5.15",
+    "phpunit/phpunit": "^9.5.4",
     "psalm/plugin-phpunit": "~0.15.1",
     "symfony/filesystem": "^4.4.0",
     "vimeo/psalm": "^4.7.2"