MB-12062: updated doc link to point to future 3.0 manual place

Change-Id: Ia0658c2b3f226c5ec01a7eb0e068df0506ae8f20
Reviewed-on: http://review.couchbase.org/41057
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Merge remote-tracking branch 'rel-3.0.0'

* rel-3.0.0:
  MB-12062: updated doc link to point to future 3.0 manual place

Change-Id: I92a301506cd11d904f01b8ece3069ed760f255a9