[TASK] Update phpstan/phpstan requirement from ^1.12.5 to ^1.12.6 (#130)

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@1.12.5...1.12.6)

---
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

@@ -21,7 +21,7 @@
         "ergebnis/composer-normalize": "^2.44.0",
         "friendsofphp/php-cs-fixer": "^3.64.0",
         "phpstan/extension-installer": "^1.4.3",
-        "phpstan/phpstan": "^1.12.5",
+        "phpstan/phpstan": "^1.12.6",
         "phpstan/phpstan-deprecation-rules": "^1.2",
         "phpstan/phpstan-phpunit": "^1.4.0",
         "phpstan/phpstan-strict-rules": "^1.6.1",