kube: use ns.Contain() for postgres and redis

This is purely for consistency. While it's objectively more "magic" than the previous convention, newcomers may be asking themselves how come namespace is passed to kube objects using ns.Contain(), but to these custom objects via cfg.namespace.

Change-Id: I061c27c74213d5481b2c7e0afd5f316e84335786
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1808
Reviewed-by: q3k <q3k@hackerspace.pl>
diff --git a/app/inventory/prod.jsonnet b/app/inventory/prod.jsonnet
index 0389223..d54ba9d 100644
--- a/app/inventory/prod.jsonnet
+++ b/app/inventory/prod.jsonnet
@@ -66,9 +66,8 @@
     storageClass:: cfg.storageClassName,
   },
 
-  postgres: postgres {
+  postgres: ns.Contain(postgres) {
     cfg+: {
-      namespace: cfg.namespace,
       appName: cfg.name,
       storageClassName: cfg.storageClassName,
       version: '15.4',