Feature #5630: Reproducible builds
It seems the reason why we did that is obsolete, see dbc479a8022142318efbe7c7fe47caacc7db5fc0.
Drop our custom update-ca-certificates.service (refs: #14756)
It was meant to re-create /etc/ssl/certs/java/cacerts at boot time since we used
to remove it at build time to make the build deterministic. We don't ship
ca-certificates-java anymore, so we don't delete /etc/ssl/certs/java/cacerts
anymore, so we don't need to re-create it.