message: Don't implicitly create ResultsNotifiers if the background thread is disabled
  Even if the user doesn't add an observer to the Results we create a Notifier
  for it to rerun the query on the background worker thread, but that isn't
  useful if the background worker thread isn't being used.
diff: @@ -884,7 +884,7 @@ bool Realm::refresh()
  bool Realm::can_deliver_notifications() const noexcept
  {
  - if (m_config.immutable()) {
  + if (m_config.immutable() || !m_config.automatic_change_notifications) {
  return false;
  }
  