Drop reference to removed glance-registry

Change-Id: I00c749d884103e1dc6a014962907c431c3a44a8c
diff --git a/.zuul.yaml b/.zuul.yaml
index e79337d..a21fff9 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -9,7 +9,6 @@
         keystone: https://opendev.org/openstack/keystone
       devstack_services:
         g-api: false
-        g-reg: false
         n-api: false
         n-api-meta: false
         n-cond: false