[Workers] Tweak code sample in timers document

Author: nzws

src/content/docs/workers/runtime-apis/nodejs/timers.mdx

@@ -18,7 +18,7 @@ and [`setImmediate`](https://nodejs.org/api/timers.html#setimmediatecallback-arg
 import timers from "node:timers";
 
 export default {
-  async fetch() {
+  async fetch(): Promise<Response> {
     console.log("first");
     const { promise: promise1, resolve: resolve1 } = Promise.withResolvers();
     const { promise: promise2, resolve: resolve2 } = Promise.withResolvers();
@@ -35,10 +35,8 @@ export default {
     await Promise.all([promise1, promise2]);
 
     return new Response("ok");
-
-}
-}
-
+  }
+} satisfies ExportedHandler<Env>;
 ```
 </TypeScriptExample>