message: Remove debugging printlns from copy out protocol
diff: @@ -25,13 +25,11 @@ pub async fn copy_out(client: &InnerClient, statement: Statement) -> Result<Copy
  async fn start(client: &InnerClient, buf: Bytes) -> Result<Responses, Error> {
  let mut responses = client.send(RequestMessages::Single(FrontendMessage::Raw(buf)))?;
  - println!("a");
  match responses.next().await? {
  Message::BindComplete => {}
  _ => return Err(Error::unexpected_message()),
  }
  - println!("b");
  match responses.next().await? {
  Message::CopyOutResponse(_) => {}
  _ => return Err(Error::unexpected_message()),
  @@ -55,7 +53,6 @@ impl Stream for CopyOutStream {
  fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
  let this = self.project();
  - println!("c");
  match ready!(this.responses.poll_next(cx)?) {
  Message::CopyData(body) => Poll::Ready(Some(Ok(body.into_bytes()))),
  Message::CopyDone => Poll::Ready(None),
  