message: Use release assertion in reset_for_testing
  This assertion attacked realm-java integration tests a lot.
  And realm-java cannot enable assertion for CI build due to the speed
  issues, this assertion is kind of turned into many ways of native
  crashes for realm-java CI.
  Change it to a release assertion so realm-java can crash earlier.
diff: @@ -212,14 +212,12 @@ void SyncManager::reset_for_testing()
  {
  std::lock_guard<std::mutex> lock(m_session_mutex);
  -#if REALM_ASSERTIONS_ENABLED
  // Callers of `SyncManager::reset_for_testing` should ensure there are no active sessions
  // prior to calling `reset_for_testing`.
  auto no_active_sessions = std::none_of(m_sessions.begin(), m_sessions.end(), [](auto& element){
  return element.second->existing_external_reference();
  });
  - REALM_ASSERT(no_active_sessions);
  -#endif
  + REALM_ASSERT_RELEASE(no_active_sessions);
  // Destroy any inactive sessions.
  // FIXME: We shouldn't have any inactive sessions at this point! Sessions are expected to
  