elliptic-curve: cleanup TODOs (#1823)

Those TODOs should have been removed in #1774

Author: baloo

elliptic-curve/src/scalar/nonzero.rs

@@ -52,7 +52,6 @@ where
         // While this method isn't constant-time, the attacker shouldn't learn
         // anything about unrelated outputs so long as `rng` is a secure `CryptoRng`.
         loop {
-            // TODO: remove after `Field::random` switches to `&mut impl RngCore`
             if let Some(result) = Self::new(Field::random(rng)).into() {
                 break result;
             }
@@ -65,7 +64,6 @@ where
         // While this method isn't constant-time, the attacker shouldn't learn
         // anything about unrelated outputs so long as `rng` is a secure `CryptoRng`.
         loop {
-            // TODO: remove after `Field::random` switches to `&mut impl RngCore`
             if let Some(result) = Self::new(Scalar::<C>::try_from_rng(rng)?).into() {
                 break Ok(result);
             }