Fixes #6554: clarified docs about AccessRule::$roles

framework/filters/AccessRule.php

@@ -42,8 +42,8 @@ class AccessRule extends Component
      * - `?`: matches a guest user (not authenticated yet)
      * - `@`: matches an authenticated user
      *
-     * Using other role names requires RBAC (Role-Based Access Control), and
-     * [[User::can()]] will be called.
+     * Alternatively RBAC (Role-Based Access Control) premission name could be specified. In this case
+     * [[User::can()]] will be called in order to check access.
      *
      * If this property is not set or empty, it means this rule applies to all roles.
      */