style: revert to styling icon with variable

risk: low

Author: zdenekornst

libs/sdk-ui-ext/src/notificationsPanel/NotificationsPanel/DefaultNotificationsPanelButton.scss

@@ -13,7 +13,7 @@
     }
 
     &__icon {
-        color: #fff;
+        --gd-icon-fill-color: #fff;
         opacity: 0.8;
         display: flex;
         align-items: center;