use async dispatch method

Prevents unresponsive dialogue on Android

src/MAUI/Maui.Samples/Samples/Location/IndoorPositioning/IndoorPositioning.xaml.cs

@@ -133,7 +133,7 @@ private void LocationDisplay_LocationChanged(object sender, Location loc)
             labelText += $"Horizontal accuracy: {string.Format("{0:0.##}", loc.HorizontalAccuracy)}m";
 
             // Update UI on the main thread.
-            Dispatcher.Dispatch(() =>
+            Dispatcher.DispatchAsync(() =>
             {
                 PositioningLabel.Text = labelText;
             });