Added a warning about multi-cells in wxGrid::DeleteRows() docs.

Currently deleting rows or columns intersecting a multi-cell is simply not
supported and results in an immediate crash.

See #4238.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70115 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/grid.h

@@ -1457,6 +1457,9 @@ public:
     /**
         Delete rows from the table.
 
+        Notice that currently deleting a row intersecting a multi-cell (see
+        SetCellSize()) is not supported and will result in a crash.
+
         @param pos
             The first row to delete.
         @param numRows