message: ff_derive: Fix a clippy issue in generated code
  This shows up as a clippy warning in the pairing crate.
diff: @@ -465,7 +465,7 @@ fn prime_field_constants_and_sqrt(
  let result = x * &z;
  x = #name::conditional_select(&result, &x, b.ct_eq(&#name::one()));
  z = z.square();
  - b = b * &z;
  + b *= &z;
  v = k;
  }
  