Require PHPCS 3.5.6 because of PHP 8

Author: kukulich

composer.json

@@ -12,7 +12,7 @@
 		"php": "^7.1 || ^8.0",
 		"dealerdirect/phpcodesniffer-composer-installer": "^0.6.2 || ^0.7",
 		"phpstan/phpdoc-parser": "0.4.5 - 0.4.9",
-		"squizlabs/php_codesniffer": "^3.5.5"
+		"squizlabs/php_codesniffer": "^3.5.6"
 	},
 	"require-dev": {
 		"phing/phing": "2.16.3",