fix bottom right corner on osx.

src/Avalonia.Controls/Primitives/PopupPositioning/ManagedPopupPositionerPopupImplHelper.cs

@@ -32,7 +32,7 @@ namespace Avalonia.Controls.Primitives.PopupPositioning
             {
                 // Popup positioner operates with abstract coordinates, but in our case they are pixel ones
                 var point = _parent.PointToScreen(default);
-                var size = PixelSize.FromSize(_parent.ClientSize, _parent.Scaling);
+                var size = TranslateSize(_parent.ClientSize);
                 return new Rect(point.X, point.Y, size.Width, size.Height);
 
             }