MB-8666: updated text for mrw settings

Change-Id: I683a770d090b0b2df0fe00c191e602f4a175d9d6
Reviewed-on: http://review.couchbase.org/28352
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>