enforce replicas for discord alertmanager agent

system-apps/monitoring/templates/discord.yaml

@@ -9,6 +9,7 @@ metadata:
     app.kubernetes.io/name: alertmanager-discord
     app.kubernetes.io/instance: {{ .Release.Name }}
 spec:
+  replicas: 1
   selector:
     matchLabels:
       app: alertmanager-discord