Remove stale hack in dashboard/graph_json.py.
Remove stale hack in dashboard/graph_json.py.

Bug: catapult:#2704
Change-Id: I66859923037ce3df10c7d2c89fc9224ec02c1d70
Reviewed-on: https://chromium-review.googlesource.com/1096287
Reviewed-by: Simon Hatch <490a224d89645d3fea983d7189ce51bde0a00c1d@chromium.org>
Commit-Queue: Ben Hayden <d3ffe0e065c2328e497bb32a07f4dcb29138ef5b@chromium.org>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult