Remove test that doesn't make sense anymore

tests/Avalonia.ReactiveUI.UnitTests/TransitioningContentControlTest.cs

@@ -12,14 +12,6 @@ namespace Avalonia.ReactiveUI.UnitTests
 {
     public class TransitioningContentControlTest
     {
-        [Fact]
-        public void Transitioning_Control_Should_Derive_Template_From_Content_Control()
-        {
-            var target = new TransitioningContentControl();
-            var stylable = (IStyledElement)target;
-            Assert.Equal(typeof(ContentControl),stylable.StyleKey);
-        }
-
         [Fact]
         public void Transitioning_Control_Template_Should_Be_Instantiated() 
         {