message: adapt example for modified dual type
diff: @@ -227,7 +227,7 @@ struct NeoHookeanMaterial
  {
  auto sigma = stress(make_tensor<dim, dim>([&](int i, int j)
  {
  - return dual<double> {dudx[i][j], ddudx[i][j]};
  + return dual<double, double> {dudx[i][j], ddudx[i][j]};
  }));
  return make_tensor<dim, dim>(
  [&](int i, int j) { return sigma[i][j].gradient; });
  