Update milagro_bls to new release (#1183)

* Update milagro_bls to new release

Signed-off-by: Kirk Baird <baird.k@outlook.com>

* Tidy up fake cryptos

Signed-off-by: Kirk Baird <baird.k@outlook.com>

* move SecretHash to bls and put plaintext back

Signed-off-by: Kirk Baird <baird.k@outlook.com>

common/eth2_interop_keypairs/tests/generation.rs

@@ -53,6 +53,6 @@ fn reference_public_keys() {
             "Reference should be 48 bytes (public key size)"
         );
 
-        assert_eq!(pair.pk.as_bytes(), reference);
+        assert_eq!(pair.pk.as_bytes().to_vec(), reference);
     });
 }