Include banner for SGW tutorials on k8s

Applies to following pages

https://docs.couchbase.com/sync-gateway/2.7/kubernetes/deploy-cluster.html
https://docs.couchbase.com/sync-gateway/2.7/kubernetes/manage-cluster.html

Please include a banner highlighting the availability of CAO 2.0.0 BETA and and mention that beta tutorials for Sync gateway on Kubernetes are now available in https://docs.couchbase.com/operator/2.0/tutorial-sync-gateway.html

(eventually, when we go GA with 2.0.0, those tutorials will supersede what's in our current section)

Reporter: Priya Rajagopal
E-mail: priya.rajagopal@couchbase.com