Does a literature survey/review paper require a 'Conclusion' section?
A good review article makes part of its contribution by doing synthesis, even theory building, as part of the paper. So I would expect you to summarise that contribution.  If you don't like calling that a Conclusion, you can call it a Summary.  But you should expect a reader to learn something from any article you write; a review just relies almost exclusively on other writers for evidence, instead of just mostly like in the case of ordinary science.