Remove "Versatile Server Nodes" section from rest-intro doc page

Remove the “Versatile Server Nodes” section from this doc page — https://docs.couchbase.com/server/current/rest-api/rest-intro.html#basic-principles

The section has been pointed out as being confusing to users. Even if the section/paragraph were corrected (remove incorrect statements, add details to clarify other statements), the information would not be helpful to users since it's mainly the UI that uses the feature to be able to redirect requests to service nodes as needed (e.g. MB-26993). So, best to remove the confusing section entirely (discussed in PM slack channel).