message: Explain why we don't need to pass `dep.artifact()`
diff: @@ -1103,7 +1103,10 @@ impl<'a, 'cfg> State<'a, 'cfg> {
  // If this is an optional dependency, and the new feature resolver
  // did not enable it, don't include it.
  if dep.is_optional() {
  - let features_for = unit_for.map_to_features_for(None);
  + // This `unit_for` is from parent dep and *SHOULD* contains its own
  + // artifact dep infomration inside `artifact_target_for_features`.
  + // So, no need to map any artifact info from an incorrect `dep.artifact()`.
  + let features_for = unit_for.map_to_features_for(IS_NO_ARTIFACT_DEP);
  if !self.is_dep_activated(pkg_id, features_for, dep.name_in_toml()) {
  return false;
  }
  