Don't hardcode lists domain

roles/mailman/templates/nginx.d.conf.j2

@@ -52,7 +52,7 @@ server {
 
     location ~ ^/(static|mailman3|archives|accounts|admin3)($|/) {
         proxy_pass http://{{ hostvars['mailman3.archlinux.org']['wireguard_address'] }};
-        proxy_set_header Host lists.archlinux.org;
+        proxy_set_header Host {{ lists_domain }};
         proxy_set_header X-Forwarded-For $remote_addr;
     }