Warning for Kafka connector when scaling down pods

It is important that we have a warning about scaling down when deploying the connector on pods to avoid scaling down by setting the replicas to lower value or 0.

Killing the connector pod can results in "rewind" the document stream and restart from an earlier point in history.

We can add it here:
https://docs.couchbase.com/kafka-connector/current/delivery-guarantees.html