doc: remove incorrect and outdated example

PR-URL: #30138
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/cluster.md

@@ -613,24 +613,6 @@ Emitted when the cluster master receives a message from any worker.
 
 See [`child_process` event: `'message'`][].
 
-Before Node.js v6.0, this event emitted only the message and the handle,
-but not the worker object, contrary to what the documentation stated.
-
-If support for older versions is required but a worker object is not
-required, it is possible to work around the discrepancy by checking the
-number of arguments:
-
-```js
-cluster.on('message', (worker, message, handle) => {
-  if (arguments.length === 2) {
-    handle = message;
-    message = worker;
-    worker = undefined;
-  }
-  // ...
-});
-```
-
 ## Event: 'online'
 <!-- YAML
 added: v0.7.0