message: Rename error code 2
diff: @@ -48,7 +48,7 @@ const ERROR_APPLICATION_CLOSE: TransportError = 12;
  pub enum Error {
  NoError,
  InternalError,
  - ServerBusy,
  + ConnectionRefused,
  FlowControlError,
  StreamLimitError,
  StreamStateError,
  @@ -101,7 +101,7 @@ impl Error {
  | Self::IdleTimeout
  | Self::PeerError(_)
  | Self::PeerApplicationError(_) => 0,
  - Self::ServerBusy => 2,
  + Self::ConnectionRefused => 2,
  Self::FlowControlError => 3,
  Self::StreamLimitError => 4,
  Self::StreamStateError => 5,
  