message: Correct comment language
diff: @@ -463,7 +463,7 @@ fn start_flush_cycle(wbuf: &Arc<Mutex<Outbound>>) -> usize {
  pub struct Message {
  /// The NATS `Subject` that this `Message` has been published to.
  pub subject: String,
  - /// The optional reply `Subject` that may be used for receiving
  + /// The optional reply `Subject` that may be used for sending
  /// responses when using the request/reply pattern.
  pub reply: Option<String>,
  /// The `Message` contents.
  