Fix approvals tests failing

Author: glennawatson

src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt

@@ -8,6 +8,7 @@
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Tests")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Uno")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Uwp")]
+[assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.WinUI")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Winforms")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Wpf")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.XamForms")]
@@ -725,6 +726,7 @@ namespace ReactiveUI
         Avalonia = 7,
         Maui = 8,
         Uwp = 9,
+        WinUI = 10,
     }
     public class Registrations
     {

src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt

@@ -8,6 +8,7 @@
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Tests")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Uno")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Uwp")]
+[assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.WinUI")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Winforms")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Wpf")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.XamForms")]
@@ -718,6 +719,7 @@ namespace ReactiveUI
         Avalonia = 7,
         Maui = 8,
         Uwp = 9,
+        WinUI = 10,
     }
     public class Registrations
     {

src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt

@@ -8,6 +8,7 @@
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Tests")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Uno")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Uwp")]
+[assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.WinUI")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Winforms")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.Wpf")]
 [assembly: System.Runtime.CompilerServices.InternalsVisibleTo("ReactiveUI.XamForms")]
@@ -718,6 +719,7 @@ namespace ReactiveUI
         Avalonia = 7,
         Maui = 8,
         Uwp = 9,
+        WinUI = 10,
     }
     public class Registrations
     {