doc: add return type of clientRequest.setTimeout

Refs: #1699
PR-URL: #8356
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Evan Lucas <[email protected]>

Author: MikeRalphson

doc/api/http.md

@@ -467,6 +467,8 @@ Once a socket is assigned to this request and is connected
 * `timeout` {Number} Milliseconds before a request is considered to be timed out.
 * `callback` {Function} Optional function to be called when a timeout occurs. Same as binding to the `timeout` event.
 
+Returns `request`.
+
 ### request.write(chunk[, encoding][, callback])
 <!-- YAML
 added: v0.1.29