doc: adjust code sample for stream.finished

PR-URL: #29983
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

Author: imcotton

doc/api/stream.md

@@ -1530,7 +1530,7 @@ If this is unwanted behavior then the returned cleanup function needs to be
 invoked in the callback:
 
 ```js
-const cleanup = finished(...streams, (err) => {
+const cleanup = finished(rs, (err) => {
   cleanup();
   // ...
 });