Add Alerta to k8s and SL models

Change-Id: I8969e225826f7e1be49e3a8dc8dcaab7975ddeb3
PROD-Related: PROD-19760
diff --git a/classes/cluster/sl-k8s-calico/stacklight/proxy.yml b/classes/cluster/sl-k8s-calico/stacklight/proxy.yml
index de4e28c..ff816c5 100644
--- a/classes/cluster/sl-k8s-calico/stacklight/proxy.yml
+++ b/classes/cluster/sl-k8s-calico/stacklight/proxy.yml
@@ -2,6 +2,7 @@
 - system.nginx.server.single
 - system.nginx.server.proxy.stacklight.grafana
 - system.nginx.server.proxy.stacklight.kibana
+- system.nginx.server.proxy.monitoring.alerta
 - system.nginx.server.proxy.monitoring.prometheus_server
 - system.nginx.server.proxy.monitoring.prometheus_alertmanager
 - system.salt.minion.cert.proxy