Fix system-config org in tools/build-image.sh
It's opendev/system-config.
@@ -83,7 +83,7 @@ fi
## add to /tmp/custom_projects.yaml:
##
## - project: openstack/project-config
-## - project: openstack/system-config
+## - project: opendev/system-config
## - project: openstack/devstack
## - project: openstack/tempest
