message: Fix comment
  h/t omershlo from Zcash Community Chat for spotting it!
diff: @@ -448,7 +448,7 @@ impl<'a, E: JubjubEngine> Circuit<E> for Spend<'a, E> {
  )?;
  }
  - // Let's compute nf = BLAKE2s(rk || rho)
  + // Let's compute nf = BLAKE2s(nk || rho)
  nf_preimage.extend(
  rho.repr(cs.namespace(|| "representation of rho"))?
  );
  