message: Remove an incorrect override of CollectionNotifier::release_data()
  Subscription::Notifier used to not have anything to release, but changes in how
  notifiers are attached to transactions means it now does, and failing to
  release the transaction leads to crashes.
diff: @@ -517,7 +517,6 @@ struct Subscription::Notifier : public _impl::CollectionNotifier {
  {
  }
  - void release_data() noexcept override { }
  void run() override
  {
  std::unique_lock<std::mutex> lock(m_mutex);
  