Bump default channel to 4.16

Author: shellyyang1989

data/data/manifests/bootkube/cvo-overrides.yaml.template

@@ -11,7 +11,7 @@ spec:
   upstream: https://amd64.origin.releases.ci.openshift.org/graph
   channel: stable-scos-4
 {{- else }}
-  channel: stable-4.14
+  channel: stable-4.16
 {{- end }}
   clusterID: {{.CVOClusterID}}
 {{- if .CVOCapabilities }}