message: Fix type in scheduled_actor::make_stage
diff: @@ -521,7 +521,7 @@ public:
  stream<typename stream_stage_trait_t<Fun>::output>
  make_stage(const stream<In>& in, Init init, Fun fun, Cleanup cleanup,
  policy::arg<Gatherer, Scatterer> policies = {}) {
  - return add_stage(in, std::make_tuple(), std::move(init), std::move(fun),
  + return make_stage(in, std::make_tuple(), std::move(init), std::move(fun),
  std::move(cleanup), policies);
  }
  