Update api.txt according to delta recovery changes.

Change-Id: I3eb054535ef6b02b4056fd1b189c69c7b85fc40b
Reviewed-on: http://review.couchbase.org/34275
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>