rm dup cookbook-openstack-network in projects.yaml

The cookbook-openstack-network stanza is listed twice in the
projects.yaml file, removing 2nd occurrence.

Change-Id: Ib960a5c1a10b54ef2bf922213db56c72b876afb6
Reviewed-on: https://review.openstack.org/35717
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Khai Do <zaro0508@gmail.com>
Approved: Monty Taylor <mordred@inaugust.com>
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Tested-by: Jenkins