fix(k3s): add namespace: monitoring to grafana-proxy-configmap

Without this, kubectl apply without -n flag lands in default namespace
instead of monitoring, leaving the live configmap with the old
knoe-auth hostname.

deploy/opentofu/k3s/manifests/knoe/grafana-proxy-configmap.yaml

@@ -2,6 +2,7 @@ apiVersion: v1
 kind: ConfigMap
 metadata:
   name: knoe-grafana-proxy-nginx
+  namespace: monitoring
 data:
   nginx.conf: |
     worker_processes  1;