Remove old manifests and replace with jsonnet build

jsonnet/alertmanager/alertmanager-main-secret.libsonnet

@@ -1,25 +1,8 @@
 local k = import "ksonnet.beta.3/k.libsonnet";
 local secret = k.core.v1.secret;
 
-local plainConfig = "global:
-  resolve_timeout: 5m
-route:
-  group_by: ['job']
-  group_wait: 30s
-  group_interval: 5m
-  repeat_interval: 12h
-  receiver: 'null'
-  routes:
-  - match:
-      alertname: DeadMansSwitch
-    receiver: 'null'
-receivers:
-- name: 'null'";
-
-local config = std.base64(plainConfig);
-
 {
-    new(namespace)::
-        secret.new("alertmanager-main", {"alertmanager.yaml": config}) +
+    new(namespace, plainConfig)::
+        secret.new("alertmanager-main", {"alertmanager.yaml": std.base64(plainConfig)}) +
           secret.mixin.metadata.withNamespace(namespace)
 }