Update zcash_primitives crate to use ff crate

zcash_primitives/src/transaction/components.rs

@@ -1,8 +1,6 @@
 use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
-use pairing::{
-    bls12_381::{Bls12, Fr, FrRepr},
-    PrimeField, PrimeFieldRepr,
-};
+use ff::{PrimeField, PrimeFieldRepr};
+use pairing::bls12_381::{Bls12, Fr, FrRepr};
 use sapling_crypto::{
     jubjub::{edwards, Unknown},
     redjubjub::{PublicKey, Signature},

zcash_primitives/src/transaction/sighash.rs

@@ -1,6 +1,6 @@
 use blake2_rfc::blake2b::Blake2b;
 use byteorder::{LittleEndian, WriteBytesExt};
-use pairing::{PrimeField, PrimeFieldRepr};
+use ff::{PrimeField, PrimeFieldRepr};
 
 use super::{
     components::{Amount, Script, TxOut},