Update phpstan/phpstan requirement from 1.12.8 to 1.12.9 (#1368)

Updates the requirements on [phpstan/phpstan](https://github.com/phpstan/phpstan) to permit the latest version.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Changelog](https://github.com/phpstan/phpstan/blob/2.0.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.12.8...1.12.9)

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

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

composer.json

@@ -46,7 +46,7 @@
     "require-dev": {
         "php-parallel-lint/php-parallel-lint": "1.4.0",
         "phpstan/extension-installer": "1.4.3",
-        "phpstan/phpstan": "1.12.8",
+        "phpstan/phpstan": "1.12.9",
         "phpstan/phpstan-phpunit": "1.4.0",
         "phpstan/phpstan-strict-rules": "1.6.1",
         "phpunit/phpunit": "9.6.21",