message: Remove superfluous `Serialize`
diff: @@ -260,7 +260,7 @@ impl<T: Item> Display for GossiperAnnouncement<T> {
  }
  /// A linear chain announcement.
  -#[derive(Debug, Serialize)]
  +#[derive(Debug)]
  pub(crate) enum LinearChainAnnouncement {
  /// A new block has been created and stored locally.
  BlockAdded(Box<Block>),
  