Missing annotations in Docker images built in CI

[chrstnbwnkl]

Starting with #5082 the docker images are built separately for arm and x86 and then later converged into one using docker manifest create. For some reason though, this newly created image does not have author or description metadata according to GitHub: https://github.com/valhalla/valhalla/pkgs/container/valhalla/350766068?tag=latest

I didn't find an immediate way to fix this, so I'll leave this here for now.