Block preview pages from seach engine

[tzach]

The PR preview process leaves both empty pages, which, unfortunately, indexed and presented by Google
http://previews.docs.scylladb.com/scylladb/20729/using-scylla/integrations/integration-kafka/

It would be best to avoid that (not sure how)

[annastuchlik]

It must be fixed in the pkg repo, so I've opened an issue: https://github.com/scylladb/scylla-pkg/issues/4945