message: mockchain: Remove impl Deserialize for Header
  It did not interop with impl Serialize.
diff: @@ -268,14 +268,6 @@ impl Readable for Header {
  }
  }
  -impl property::Deserialize for Header {
  - type Error = std::io::Error;
  - fn deserialize<R: std::io::BufRead>(reader: R) -> Result<Self, Self::Error> {
  - let raw = HeaderRaw::deserialize(reader)?;
  - read_from_raw(raw.as_ref())
  - }
  -}
  -
  impl property::Header for Header {
  type Id = HeaderHash;
  type Date = BlockDate;
  