Incorrect description for AnalyticsReader

The description of the AnalyticsReader role contains then sentence:

"This is defined as a global role because as multiple buckets may be combined into a single shadow dataset."

However, this is not a correct statement as datasets can only shadow a subset of a single bucket. I think that we should just remove the sentence from the docs (starting at 6.0).

Reporter: Till
E-mail: till@couchbase.com