Revert "staging: enable IPv4 diplonat (UPnP) for corrin site"

This reverts commit 22dba1f35c.

This site is now also a production site, so from now on UPnP will only be
configured from the production cluster.

cluster/staging/app/core/deploy/diplonat.hcl

@@ -54,7 +54,7 @@ job "core-diplonat" {
         data = <<EOH
 DIPLONAT_REFRESH_TIME=60
 DIPLONAT_EXPIRATION_TIME=300
-DIPLONAT_IPV6_ONLY={{ $site := env "meta.site" }}{{ if eq $site "corrin" }}false{{ else }}true{{ end }}
+DIPLONAT_IPV6_ONLY=true
 DIPLONAT_CONSUL_NODE_NAME={{ env "attr.unique.hostname" }}
 DIPLONAT_CONSUL_URL=https://localhost:8501
 DIPLONAT_CONSUL_CA_CERT=/etc/diplonat/consul-ca.crt