message: Add missing return in type inspection example
diff: @@ -458,7 +458,7 @@ an ``enum class`` otherwise.
  if (f.has_human_readable_format()) {
  auto get = [&x] { return to_string(x); };
  auto set = [&x](std::string str) { return parse(str, x); };
  - f.object(x).fields(f.field("value", get, set));
  + return f.object(x).fields(f.field("value", get, set));
  } else {
  using default_impl = caf::default_inspector_access<weekday>;
  return default_impl::apply_object(f, x);
  