misc: remove unused ViewModel references from demo pages.

demo/Ursa.Demo/Pages/LoadingDemo.axaml.cs

@@ -1,5 +1,4 @@
 using Avalonia.Controls;
-using Avalonia.Markup.Xaml;
 
 namespace Ursa.Demo.Pages;
 
@@ -9,9 +8,4 @@ public partial class LoadingDemo : UserControl
     {
         InitializeComponent();
     }
-
-    private void InitializeComponent()
-    {
-        AvaloniaXamlLoader.Load(this);
-    }
 }