doc: remove unused import from sample code

The `node:path` module is referenced in a code snippet that doesn't
actually use it.

PR-URL: nodejs#55570
Reviewed-By: Raz Luvaton <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>

Author: blended-bram

doc/api/async_context.md

@@ -626,7 +626,6 @@ a Worker pool around it could use the following structure:
 ```mjs
 import { AsyncResource } from 'node:async_hooks';
 import { EventEmitter } from 'node:events';
-import path from 'node:path';
 import { Worker } from 'node:worker_threads';
 
 const kTaskInfo = Symbol('kTaskInfo');