doc: fix http2 example with rstWithCancel

Replace the non-existent method rstStreamWithCancel with rstWithCancel

PR-URL: #16365
Reviewed-By: Joyee Cheung <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Anatoli Papirovski <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

doc/api/http2.md

@@ -817,7 +817,7 @@ const client = http2.connect('http://example.org:8000');
 const req = client.request({ ':path': '/' });
 
 // Cancel the stream if there's no activity after 5 seconds
-req.setTimeout(5000, () => req.rstStreamWithCancel());
+req.setTimeout(5000, () => req.rstWithCancel());
 ```
 
 #### http2stream.state