message: Remove some outdated comment
diff: @@ -12,7 +12,6 @@ pub struct Extern<S: Storage, A: Api> {
  }
  // ReadonlyStorage is access to the contracts persistent data store
  -//pub trait ReadonlyStorage: Clone {
  pub trait ReadonlyStorage {
  fn get(&self, key: &[u8]) -> Option<Vec<u8>>;
  }
  