Bump squizlabs/php_codesniffer to ~3.13.6 (CVE-2026-67434)

Addresses high severity CVE-2026-67434 affecting php_codesniffer < 3.13.6.

Author: rtoczek

composer.json

@@ -26,7 +26,7 @@
         "phpunit/phpunit": "^9.6.33",
         "sebastian/phpcpd": "^6.0.3",
         "slevomat/coding-standard": "~6.4.1",
-        "squizlabs/php_codesniffer": "~3.7.2",
+        "squizlabs/php_codesniffer": "~3.13.6",
         "phpstan/phpstan-phpunit": "^1.1.1"
     },
     "repositories": [