Update dependency phpstan/phpstan to ^2.1.56

| datasource | package         | from   | to     |
| ---------- | --------------- | ------ | ------ |
| packagist  | phpstan/phpstan | 2.1.55 | 2.1.56 |

Author: renovate[bot]

composer.json

@@ -14,7 +14,7 @@
         "php": "~8.4.0 || ~8.5.0"
     },
     "require-dev": {
-        "phpstan/phpstan": "^2.1.55",
+        "phpstan/phpstan": "^2.1.56",
         "phpstan/phpstan-phpunit": "^2.0.16",
         "phpstan/phpstan-strict-rules": "^2.0.11",
         "phpunit/phpunit": "^13.1.12",