[php-actions/composer] use composer version 2.x

based on https://github.com/php-actions/composer#using-different-versions-of-php-or-composer

Author: Un1matr1x

.github/workflows/validate.yaml

@@ -14,4 +14,4 @@ jobs:
         with:
           command: validate
           php_version: "8.0.1"
-          version: "2.2"
+          version: 2.x