Update phpstan/phpstan requirement from 1.12.1 to 1.12.6

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@1.12.1...1.12.6)

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

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

composer.json

@@ -33,7 +33,7 @@
     "diablomedia/php-cs-fixer-config": "^2.1.0",
     "friendsofphp/php-cs-fixer": "3.6.0",
     "phorgeit/arcanist": "1.0.0",
-    "phpstan/phpstan": "1.12.1"
+    "phpstan/phpstan": "1.12.6"
   },
   "autoload-dev": {
     "classmap": [