Meaningful changes from aggressive-clippy

I do want to enable a few specific lints, yet aggressive-clippy as a whole
isn't worthwhile.

crypto/ed448/src/backend.rs

@@ -80,7 +80,7 @@ macro_rules! field {
     $DELTA: expr,
   ) => {
     use core::{
-      ops::{DerefMut, Add, AddAssign, Neg, Sub, SubAssign, Mul, MulAssign},
+      ops::{Add, AddAssign, Neg, Sub, SubAssign, Mul, MulAssign},
       iter::{Sum, Product},
     };
 
@@ -150,7 +150,7 @@ macro_rules! field {
         let mut bits = 0;
         for (i, mut bit) in other.to_le_bits().iter_mut().rev().enumerate() {
           bits <<= 1;
-          let mut bit = u8_from_bool(bit.deref_mut());
+          let mut bit = u8_from_bool(&mut bit);
           bits |= bit;
           bit.zeroize();