3.6.8 Simplify offset splitting

This wasn't done prior to be 'leaderless', as now the participant with the
lowest ID has an extra step, yet this is still trivial. There's also notable
performance benefits to not taking the previous dividing approach, which
performed an exp.

crypto/frost/src/sign.rs

@@ -318,7 +318,7 @@ impl<C: Curve, A: Algorithm<C>> SignMachine<A::Signature> for AlgorithmSignMachi
       }
     }
 
-    let view = self.params.keys.view(&included).unwrap();
+    let view = self.params.keys.view(included.clone()).unwrap();
     validate_map(&preprocesses, &included, multisig_params.i())?;
 
     {