Disable the popupwindow close test for nodejs

Unfortunately in the CI the test runs with Qt, where send_mouse_click in
the test will send the event to the main QWindow not the popup.

We can't select the testing backend because it's not published and
we can't make the nodejs crate depend on it for initialization.

tests/cases/elements/popupwindow_close.slint

@@ -152,7 +152,7 @@ slint_testing::send_mouse_click(&instance, 5., 5.);
 assert_eq(instance.get_click_count(), 1);
 ```
 
-```js
+```disable-because-nodejs-runs-with-qt-and-send-mouse-click-wont-send-to-popup-qwindow
 var instance = new slint.TestCase({});
 
 assert.equal(instance.click_count, 0);