[OSDOCS-15001]: Add MCE content source to HCP example

Author: lahinson

modules/hcp-hc-objects.adoc

@@ -127,6 +127,10 @@ spec:
     mirrors:
     - registry.<dns.base.domain.name>:5000/openshift/release-images <5>
   - mirrors:
+    - registry.<dns.base.domain.name>:5000/openshift/release-images <5>
+  - source: registry.redhat.io/multicluster-engine
+    mirrors:
+    - registry.<dns.base.domain.name>:5000/openshift/multicluster-engine <5>
   # ...
   autoscaling: {}
   controllerAvailabilityPolicy: SingleReplica