doc: fix triggerAsyncId() comment in async_hooks example

The connection-callback comment claims triggerAsyncId() returns the
asyncId of "conn". It actually returns the server's own triggerAsyncId,
because the callback runs in the execution scope of the server's
MakeCallback() — as the sibling executionAsyncId() example already
explains. Mirror that comment.

Fixes: #21078
Signed-off-by: Julian Soreavis <julian.soreavis@gmail.com>
PR-URL: #64583
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

Author: soreavis

doc/api/async_hooks.md

@@ -814,9 +814,9 @@ See the section on [promise execution tracking][].
 
 ```js
 const server = net.createServer((conn) => {
-  // The resource that caused (or triggered) this callback to be called
-  // was that of the new connection. Thus the return value of triggerAsyncId()
-  // is the asyncId of "conn".
+  // Returns the triggerAsyncId of the server, not of the new connection,
+  // because the callback runs in the execution scope of the server's
+  // MakeCallback().
   async_hooks.triggerAsyncId();
 
 }).listen(port, () => {