Remove extern crate (#5922)

* Remove extern crate

common/eth2_interop_keypairs/src/lib.rs

@@ -16,11 +16,9 @@
 //!
 //! This implementation passes the [reference implementation
 //! tests](https://github.com/ethereum/eth2.0-pm/blob/6e41fcf383ebeb5125938850d8e9b4e9888389b4/interop/mocked_start/keygen_test_vector.yaml).
-#[macro_use]
-extern crate lazy_static;
-
 use bls::{Keypair, PublicKey, SecretKey};
 use ethereum_hashing::hash;
+use lazy_static::lazy_static;
 use num_bigint::BigUint;
 use serde::{Deserialize, Serialize};
 use std::fs::File;