puppet: Make zulip::base include zulip::apt_repository.

There was likely more dependency complexity prior to 97766102df, but
there is now no reason to require that consumers explicitly include
zulip::apt_repository.

puppet/zulip_ops/manifests/base.pp

@@ -1,6 +1,5 @@
 class zulip_ops::base {
   include zulip::base
-  include zulip::apt_repository
   include zulip_ops::munin_node
 
   $org_base_packages = [# Management for our systems