message: Remove unused dummy Sha224
diff: -//! Dummy Sha-256 and Sha-224 Digest impls.
  -//! These digests store/accept an already hashed value of the proper length.
  +//! Dummy Sha-256 Digest impl.
  +//! This digest stores/accepts an already hashed value of the proper length.
  //! Just to comply with the Digest contract.
  //!
  //! Adapted from `sha2` [sha256.rs](https://github.com/RustCrypto/hashes/blob/master/sha2/src/sha256.rs)
  -use sha2::digest::consts::{U28, U32};
  +use sha2::digest::consts::U32;
  use sha2::digest::generic_array::GenericArray;
  use sha2::digest::{FixedOutputDirty, Reset, Update};
  @@ -43,38 +43,3 @@ impl Reset for IdentitySha256 {
  *self = Self::default();
  }
  }
  -
  -/// The SHA-224 identity container.
  -#[derive(Clone)]
  -pub struct IdentitySha224 {
  - array: GenericArray<u8, U28>,
  -}
  -
  -impl Default for IdentitySha224 {
  - fn default() -> Self {
  - IdentitySha224 {
  - array: GenericArray::default(),
  - }
  - }
  -}
  -
  -impl Update for IdentitySha224 {
  - fn update(&mut self, hash: impl AsRef<[u8]>) {
  - assert_eq!(hash.as_ref().len(), 28);
  - self.array = *GenericArray::from_slice(hash.as_ref());
  - }
  -}
  -
  -impl FixedOutputDirty for IdentitySha224 {
  - type OutputSize = U28;
  -
  - fn finalize_into_dirty(&mut self, out: &mut digest::Output<Self>) {
  - *out = self.array;
  - }
  -}
  -
  -impl Reset for IdentitySha224 {
  - fn reset(&mut self) {
  - *self = Self::default();
  - }
  -}
  