docs: apt-get update before apt-get install to avoid 404 on old packages
docs: apt-get update before apt-get install to avoid 404 on old packages

heartsucker/securedrop,ehartsuyker/securedrop,conorsch/securedrop,conorsch/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,heartsucker/securedrop,conorsch/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,conorsch/securedrop,ehartsuyker/securedrop,conorsch/securedrop,ehartsuyker/securedrop