Completes U4-2929 Finish obsoleting the remaining legacy property editors

src/umbraco.editorControls/XPathCheckBoxList/XPathCheckBoxList.cs

@@ -1,8 +1,10 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using umbraco.NodeFactory;
 
 namespace umbraco.editorControls.XPathCheckBoxList
 {
+    [Obsolete("IDataType and all other references to the legacy property editors are no longer used this will be removed from the codebase in future versions")]
     public class XPathCheckBoxList : uQuery.IGetProperty
     {
         public XPathCheckBoxList()