composer(deps-dev): update phpstan/phpstan requirement

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@1.12.7...1.12.8)

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

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

composer.json

@@ -40,7 +40,7 @@
   },
   "require-dev": {
     "phpstan/extension-installer": "^1.4.3",
-    "phpstan/phpstan": "^1.12.7",
+    "phpstan/phpstan": "^1.12.8",
     "phpstan/phpstan-deprecation-rules": "^1.2.1",
     "rector/type-perfect": "^1.0.0",
     "symplify/phpstan-rules": "^13.0.1",