Update slevomat/coding-standard to ^8.0

Author: tomas-novotny

composer.json

@@ -20,7 +20,7 @@
     "require": {
         "php": "^7.4 || ^8.0",
         "dealerdirect/phpcodesniffer-composer-installer": "^0.7.2",
-        "doctrine/coding-standard": "^9.0"
+        "doctrine/coding-standard": "9.0.x-dev"
     },
     "config": {
         "sort-packages": true,