doc: use any for worker_threads.Worker 'error' event argument err

A worker thread can throw anything via the `throw` keyword, which gets
passed directly to 'error' event listeners. The event listener should
not assume it is an `Error` object.

PR-URL: #60300
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

Author: jonasgeiler

doc/api/worker_threads.md

@@ -1717,7 +1717,7 @@ changes:
 added: v10.5.0
 -->
 
-* `err` {Error}
+* `err` {any}
 
 The `'error'` event is emitted if the worker thread throws an uncaught
 exception. In that case, the worker is terminated.