Improve wxPGChoices::Set() documentation too

Refer to Add() and use @overload rather than duplicating the
description.

interface/wx/propgrid/property.h

@@ -2662,11 +2662,13 @@ public:
 
     /**
         Sets contents from lists of strings and values.
+
+        This is similar to calling Clear() and the corresponding overload of Add().
     */
     void Set( const wxChar** labels, const long* values = NULL );
 
     /**
-        Sets contents from lists of strings and values.
+        @overload
      */
     void Set( const wxArrayString& labels, const wxArrayInt& values = wxArrayInt() );