message: Make UnverifiedBlock private.
diff: @@ -1275,10 +1275,10 @@ pub struct Block {
  /// A temporary copy of a block that has not been validated yet.
  #[derive(Debug, Deserialize)]
  -pub(crate) struct UnverifiedBlock {
  - pub(crate) hash: BlockHash,
  - pub(crate) header: BlockHeader,
  - pub(crate) body: BlockBody,
  +struct UnverifiedBlock {
  + hash: BlockHash,
  + header: BlockHeader,
  + body: BlockBody,
  }
  impl UnverifiedBlock {
  