Add logging CNAME to monitoring

This allows us to get proper certificates for loki which will run on logging.archlinux.org
on the same machine as monitoring.archlinux.org.

tf-stage1/archlinux.tf

@@ -291,6 +291,7 @@ locals {
     rsync         = { value = "gemini" }
     sources       = { value = "gemini" }
     "static.conf" = { value = "redirect" }
+    logging       = { value = "monitoring" }
     status        = { value = "stats.uptimerobot.com." }
     svn           = { value = "gemini" }