Update phpstan/phpstan requirement from ^2.2.3 to ^2.2.8

Updates the requirements on [phpstan/phpstan](https://github.com/phpstan/phpstan-phar-composer-source) to permit the latest version.
- [Commits](https://github.com/phpstan/phpstan-phar-composer-source/commits)

---
updated-dependencies:
- dependency-name: phpstan/phpstan
  dependency-version: 2.2.8
  dependency-type: direct:development
...

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

Author: dependabot[bot]

composer.json

@@ -17,7 +17,7 @@
   },
   "require-dev": {
     "doctrine/coding-standard": "^14.0",
-    "phpstan/phpstan": "^2.2.3",
+    "phpstan/phpstan": "^2.2.8",
     "phpunit/phpunit": "^12.5.6"
   },
   "autoload": {