ff: Remove Ord bound from PrimeField

ff_derive still implements Ord and PartialOrd for the fields it
implements, because pairing::bls12_381 internally assumes that those are
implemented. Once we delete that implementation, we will remove the Ord
and PartialOrd implementations from ff_derive.

src/groth16/tests/dummy_engine.rs

@@ -3,7 +3,6 @@ use group::{CurveAffine, CurveProjective, EncodedPoint, GroupDecodingError};
 use pairing::{Engine, PairingCurveAffine};
 
 use rand_core::RngCore;
-use std::cmp::Ordering;
 use std::fmt;
 use std::num::Wrapping;
 use std::ops::{Add, AddAssign, BitAnd, Mul, MulAssign, Neg, Shr, Sub, SubAssign};
@@ -48,18 +47,6 @@ impl ConditionallySelectable for Fr {
     }
 }
 
-impl Ord for Fr {
-    fn cmp(&self, other: &Fr) -> Ordering {
-        (self.0).0.cmp(&(other.0).0)
-    }
-}
-
-impl PartialOrd for Fr {
-    fn partial_cmp(&self, other: &Fr) -> Option<Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
 impl Neg for Fr {
     type Output = Self;