message: remove non needed Arc leadership in the State
diff: use crate::block::{BlockContents, Message};
  use crate::ledger::Ledger;
  -use crate::{block, leadership, ledger, setting};
  -use chain_core::property;
  -use std::sync::Arc;
  -
  -pub(crate) type Leadership = Arc<
  - Box<
  - dyn property::LeaderSelection<
  - Block = block::Block,
  - Error = leadership::Error,
  - LeaderId = leadership::PublicLeader,
  - >,
  - >,
  ->;
  +use crate::{ledger, setting};
  pub struct State {
  pub(crate) ledger: Ledger,
  pub(crate) settings: setting::Settings,
  - pub(crate) leadership: Leadership,
  }
  pub enum Error {
  @@ -49,7 +36,6 @@ impl State {
  Ok(State {
  ledger: new_ledger,
  settings: self.settings.clone(),
  - leadership: self.leadership.clone(),
  })
  }
  }
  @@ -59,7 +45,6 @@ impl State {
  State {
  ledger: Ledger::new(),
  settings: setting::Settings::new(),
  - leadership: Arc::new(Box::new(leadership::none::NoLeadership)),
  }
  }
  }
  