Fixes missing unit scope

Fixes missing unit scope

Author: chuacw

Demos/Advanced/VisibilityDemo.pas

@@ -10,9 +10,10 @@
 interface
 
 uses
-  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
-  StdCtrls, VirtualTrees, ComCtrls, ExtCtrls, ImgList, VirtualTrees.Types,
-  VirtualTrees.BaseAncestorVCL, VirtualTrees.BaseTree, VirtualTrees.AncestorVCL;
+  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Classes, Vcl.Graphics,
+  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, VirtualTrees, Vcl.ComCtrls,
+  Vcl.ExtCtrls, Vcl.ImgList, VirtualTrees.Types, VirtualTrees.BaseAncestorVCL,
+  VirtualTrees.BaseTree, VirtualTrees.AncestorVCL;
 
 type
   TVisibilityForm = class(TForm)