message: core: don't notify on timeout
  We only notify on new systems here now.
diff: @@ -450,12 +450,6 @@ void MavsdkImpl::notify_on_timeout(const uint64_t uuid)
  if (_on_timeout_callback) {
  _on_timeout_callback(uuid);
  }
  -
  - std::lock_guard<std::mutex> lock(_new_system_callback_mutex);
  - if (_new_system_callback) {
  - auto temp_callback = _new_system_callback;
  - call_user_callback([temp_callback]() { temp_callback(); });
  - }
  }
  void MavsdkImpl::subscribe_on_new_system(Mavsdk::NewSystemCallback callback)
  