puppet: Move logrotate config into app_frontend_base.

7c023042cf moved the logrotate configuration to being a templated
file, from a static file, but missed that the static file was still
referenced from `zulip_ops::app_frontend`; it only updated
`zulip::profile::app_frontend`.  This caused errors in applying puppet
on any `zulip_ops::app_frontend` host.

Prior to 7c023042cf, the Puppet role was identical between those two
classes; deduplicate the rule by moving the updated template
definition into `zulip::app_frontend_base` which is common to those
two classes and not used in any other classes.

puppet/zulip_ops/manifests/app_frontend.pp

@@ -16,14 +16,6 @@ class zulip_ops::app_frontend {
   zulip_ops::firewall_allow{ 'http': }
   zulip_ops::firewall_allow{ 'https': }
 
-  file { '/etc/logrotate.d/zulip':
-    ensure => file,
-    owner  => 'root',
-    group  => 'root',
-    mode   => '0644',
-    source => 'puppet:///modules/zulip/logrotate/zulip',
-  }
-
   file { "${zulip::common::supervisor_conf_dir}/redis_tunnel.conf":
     ensure  => file,
     require => Package['supervisor', 'autossh'],