Updated openstack/openstack
Project: openstack/pycadf  39aeafdec66011606a1f9603be1ff390e02bd855

Fix a grammatical error in contributing doc

I noticed a small grammatical error in the contributing
doc so I went ahead and fixed it.

Change-Id: Idb36271fa37f7e970e4d2698f9817cbdd63f0269