In ast doc, update 'below' to 'above' (GH-94967)


The included asdl file was moved from 'below' to 'above' in 3.9.
(cherry picked from commit 7b617be4ab6df871cfa9d2127908cb1373578dc0)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
1 file changed