fix: Removing app.xaml.host.cs

src/Uno.Extensions.Templates/content/unoapp-extensions/MyExtensionsApp.UI/MyExtensionsApp.UI.projitems

@@ -18,9 +18,6 @@
     <Compile Include="$(MSBuildThisFileDirectory)App.xaml.cs">
       <DependentUpon>App.xaml</DependentUpon>
     </Compile>
-    <Compile Include="$(MSBuildThisFileDirectory)App.xaml.host.cs">
-      <DependentUpon>App.xaml</DependentUpon>
-    </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Views\Shell.xaml.cs">
       <DependentUpon>Shell.xaml</DependentUpon>
     </Compile>