Remove unnecessary ClearOnVisibleFalse property.

Terminal.Gui/Views/Scroll.cs

@@ -17,7 +17,6 @@ public class Scroll : View
     public Scroll ()
     {
         WantContinuousButtonPressed = true;
-        //ClearOnVisibleFalse = false;
         CanFocus = false;
         Orientation = Orientation.Vertical;
         Width = Dim.Auto (DimAutoStyle.Content, 1);

UnitTests/Views/ScrollTests.cs

@@ -186,7 +186,6 @@ public class ScrollTests
     {
         var scroll = new Scroll ();
         Assert.True (scroll.WantContinuousButtonPressed);
-        Assert.False (scroll.ClearOnVisibleFalse);
         Assert.False (scroll.CanFocus);
         Assert.Equal (Orientation.Vertical, scroll.Orientation);
         Assert.Equal (0, scroll.Size);