fixed runtime xaml load failure

src/core/Microsoft.PowerToys.Settings.UI.Island/App.xaml.cs

@@ -1,17 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Configuration;
-using System.Data;
-using System.Linq;
-using System.Threading.Tasks;
-using System.Windows;
-
-namespace SettingsRunner
-{
-    /// <summary>
-    /// Interaction logic for App.xaml
-    /// </summary>
-    public partial class App : Application
-    {
-    }
-}