feat: migrate away from transitional packages

Several of the packages being installed were actually transitional packages, that is, the package itself is either a complete no-op (since the package is already installed), or else the package only exists to depend on another package of a new name (to support people who are running older operating systems).

For the former, we can drop the dependency entirely, and for the latter we should use the new package name directly.

contrib/images/digitalocean/in_parts/011-docker

@@ -4,8 +4,7 @@ set -o errexit
 
 export DEBIAN_FRONTEND=noninteractive
 
-pkgs=(apt-transport-https
-  ca-certificates
+pkgs=(ca-certificates
   curl
   jq
   linux-image-extra-virtual

contrib/images/digitalocean/in_parts/012-dokku-packages

@@ -24,7 +24,7 @@ pkgs=(apache2-utils
   unzip
 
   nginx
-  dnsutils
+  bind9-dnsutils
   cgroupfs-mount
   cgroup-lite
   sudo