URL for GPU Hackathon changed with latest update

With merge request !187 (merged) the url for the hackathon event page changed from https://software.hifis.net/events/2020/01/20/helmholtz-gpu-hackathon to https://software.hifis.net/events/2020/03/09/helmholtz-gpu-hackathon. The old URL has been used in announcements. Please change it back or provide a redirect