Update phpstan/phpstan-phpunit requirement from 0.12.17 to 0.12.18

Updates the requirements on [phpstan/phpstan-phpunit](https://github.com/phpstan/phpstan-phpunit) to permit the latest version.
- [Release notes](https://github.com/phpstan/phpstan-phpunit/releases)
- [Commits](phpstan/phpstan-phpunit@0.12.17...0.12.18)

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

Author: dependabot-preview[bot]

composer.json

@@ -22,7 +22,7 @@
         "infection/infection": "^0.20.2",
         "phpstan/extension-installer": "^1.1",
         "phpstan/phpstan": "0.12.68",
-        "phpstan/phpstan-phpunit": "0.12.17",
+        "phpstan/phpstan-phpunit": "0.12.18",
         "phpstan/phpstan-strict-rules": "0.12.9",
         "phpunit/phpunit": "^9.2",
         "psalm/plugin-phpunit": "^0.15.0",