doc: adjust changelog to clarify `client` revert

PR-URL: https://github.com/nodejs/io.js/pull/1859


Reviewed-By: Brendan Ashworth <brendan.ashworth@me.com>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>