fix(ui5-notification-list): corrects misusage of ui5-toast

The sample in the playground used toast.show() method
which was deprecated and this resulted in the ui5-toast
not showing in the playground sample

Fixes: #10526

packages/website/docs/_samples/fiori/NotificationList/Basic/main.js

@@ -14,5 +14,5 @@ notificationList.addEventListener("item-close", e => {
 
 menuWithActions.addEventListener("ui5-item-click", function(event) {
     wcToast.textContent = "Menu button '" + event.detail.text + "' pressed" + " on Notification List Item with id '" + event.target.parentElement.id + "'.";
-    wcToast.show();
+    wcToast.open = true;
 });