message: A WebTransport session should be rejected with 404
diff: @@ -867,7 +867,7 @@ impl Http3Connection {
  (Some(s), Some(_r), false) => {
  if s.http_stream()
  .ok_or(Error::InvalidStreamId)?
  - .send_headers(&[Header::new(":status", "400")], conn)
  + .send_headers(&[Header::new(":status", "404")], conn)
  .is_ok()
  {
  mem::drop(self.stream_close_send(conn, stream_id));
  