Remove `UseDataGrid` since DataGrid works without that now.

samples/ControlCatalog.Desktop/Program.cs

@@ -26,8 +26,7 @@ namespace ControlCatalog
             => AppBuilder.Configure<App>()
                 .LogToDebug()
                 .UsePlatformDetect()
-                .UseReactiveUI()
-                .UseDataGrid();
+                .UseReactiveUI();
 
         private static void ConfigureAssetAssembly(AppBuilder builder)
         {

samples/ControlCatalog.NetCore/Program.cs

@@ -47,8 +47,7 @@ namespace ControlCatalog.NetCore
             => AppBuilder.Configure<App>()
                 .UsePlatformDetect()
                 .UseSkia()
-                .UseReactiveUI()
-                .UseDataGrid();
+                .UseReactiveUI();
 
         static void ConsoleSilencer()
         {

samples/interop/WindowsInteropTest/Program.cs

@@ -15,7 +15,7 @@ namespace WindowsInteropTest
         {
             System.Windows.Forms.Application.EnableVisualStyles();
             System.Windows.Forms.Application.SetCompatibleTextRenderingDefault(false);
-            AppBuilder.Configure<App>().UseWin32().UseDirect2D1().UseDataGrid().SetupWithoutStarting();
+            AppBuilder.Configure<App>().UseWin32().UseDirect2D1().SetupWithoutStarting();
             System.Windows.Forms.Application.Run(new SelectorForm());
         }
     }

src/Avalonia.Controls.DataGrid/AppBuilderExtensions.cs

@@ -1,20 +0,0 @@
-// Copyright (c) The Avalonia Project. All rights reserved.
-// Licensed under the MIT license. See licence.md file in the project root for full license information.
-
-using Avalonia.Controls;
-using Avalonia.Threading;
-
-namespace Avalonia
-{
-    public static class AppBuilderExtensions
-    {
-        public static TAppBuilder UseDataGrid<TAppBuilder>(this TAppBuilder builder)
-            where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
-        {
-            // Portable.Xaml doesn't correctly load referenced assemblies and so doesn't
-            // find `DataGrid` when loading XAML. Call this method from AppBuilder as a
-            // temporary workaround until we fix XAML.
-            return builder;
-        }
-    }
-}