Drop reference to removed services

glance-registry, nova-consoleauth and nova-objectstore were all removed
multiple cycles ago.

Change-Id: I5f6cfd4fc62f9bda9cd2424f83545623d61ad378

.zuul.yaml

@@ -218,15 +218,12 @@
         key: true
         # Glance services
         g-api: true
-        g-reg: true
         # Nova services
         n-api: true
         n-api-meta: true
-        n-cauth: true
         n-cond: true
         n-cpu: true
         n-novnc: true
-        n-obj: true
         n-sch: true
         placement-api: true
         # Neutron services