[releases] Dropping my releases core/release-manager hat

Hello folks, I am sad to announce that, while super motivated to keep helping the team, I cannot reliably and consistantly do my duties of core in the releases team, due to my current duties at work. It's been a while I haven't significantly helped the release team, and the team deserve all the transparency and clarity it can get about its contributors. It's time for me to step down. It's been a pleasure to help the team while it lasted. If you are looking for a team to get involved in OpenStack, make no mistake, the release team is awesome. Thank you everyone in the team, you were all amazing and so welcoming :) Regards, Jean-Philippe Evrard (evrardjp)