message: refactor(core): More clippy lints..
diff: @@ -36,7 +36,7 @@ use tokio::runtime::Runtime;
  use tokio::sync::mpsc::Sender;
  use tokio::sync::Mutex as AsyncMutex;
  -use jsonrpc_core::serde_json::{self,};
  +use jsonrpc_core::serde_json;
  use super::TransportHandler;
  @@ -378,7 +378,7 @@ mod tests {
  let listen_to_state_msg = json!({
  "msg_type": "ListenToState",
  - "state_id": 1 as u16,
  + "state_id": 1,
  "trigger": "client"
  })
  .to_string();
  