build(deps-dev): bump phpstan/phpstan from 1.12.8 to 1.12.9

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 1.12.8 to 1.12.9.
- [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
  update-type: version-update:semver-patch
...

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

composer.json

@@ -8,7 +8,7 @@
     "ext-igbinary": "*"
   },
   "require-dev": {
-    "phpstan/phpstan": "1.12.8"
+    "phpstan/phpstan": "1.12.9"
   },
   "autoload": {
     "psr-4": {