Some changes on "Get root Certificates"

A couple of issues, in my opinion, are on "Get Root Certificates" page
https://docs-staging.couchbase.com/server/7.1/rest-api/get-trusted-cas.html

1. Firstly, in the "Description" section of that page, we mention that 
"Either the Full Admin or the Security Admin role is required."

Technically, this isn't true because GET /pools/default/trustedCAs is available for unauthorised users as well. But of-course, some fields in the response are masked for unauthorised users. 
Please refer https://issues.couchbase.com/browse/MB-50495

2. In the Responses section we mention

Authentication with inadequate credentials returns 403 Forbidden, and an error message such as: {"message":"Forbidden. User needs the following permissions","permissions":["cluster.admin.security!write"]}.

I don't think we can get 403 status code as the endpoint is open for all as I mention in the first point. 

3. For the "Example" section, a good idea could be that we show the response of both unauthorised users and authorised users (since both kind of users receive a valid response from ns-server for the above endpoint)