Remove stale references from projects.yaml

We don't necessarily need to delete the repo - but we don't exactly need to
keep it in the lists of things we process.

Change-Id: Ie18c2ca57435bea485b41f46d9bcf6772ec09bbc
Reviewed-on: https://review.openstack.org/19873
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins