Remove proto_tree_add_text from gryphon dissector.

Change-Id: If9f85a6cda483c5b89f9bee3524502b888ccb1d1
Reviewed-on: https://code.wireshark.org/review/3676
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Reviewed-by: Anders Broman <a.broman58@gmail.com>