ng.client: don't cache https://

apt-cacher/ng/files/client.conf

@@ -1,2 +1,3 @@
 {% from "apt-cacher/ng/map.jinja" import apt_cacher_ng with context %}
 Acquire::http::Proxy "http://{{ apt_cacher_ng.server_address }}:{{ apt_cacher_ng.server_port }}";
+Acquire::https::Proxy "DIRECT";