doc: fixed variable names in queueMicrotask example

fixed variable name in queueMicrotask where url variable was used
instead of key

PR-URL: #39634
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Harshitha K P <harshitha014@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

doc/api/globals.md

@@ -242,7 +242,7 @@ within each turn of the Node.js event loop.
 // before any other promise jobs.
 
 DataHandler.prototype.load = async function load(key) {
-  const hit = this._cache.get(url);
+  const hit = this._cache.get(key);
   if (hit !== undefined) {
     queueMicrotask(() => {
       this.emit('load', hit);
@@ -251,7 +251,7 @@ DataHandler.prototype.load = async function load(key) {
   }
 
   const data = await fetchData(key);
-  this._cache.set(url, data);
+  this._cache.set(key, data);
   this.emit('load', data);
 };
 ```