fix(gitops): omit targetNamespace on root cluster-sync to preserve per-resource namespaces (#36)

### Summary of Changes

- Removed `targetNamespace` from root `cluster-sync` Kustomization so
each application and infrastructure component preserves its own declared
namespace (`com-ermnvldmr`, `cert-manager`, etc.).

ci/cloud-init/user-data.template.yaml

@@ -203,7 +203,6 @@ EOF_DNS
         namespace: flux-system
       spec:
         interval: 5m
-        targetNamespace: com-ermnvldmr
         sourceRef:
           kind: GitRepository
           name: ermnvldmr-repo

ci/k8s/clusters/production/flux-system/gotk-sync.yaml

@@ -16,7 +16,6 @@ metadata:
   namespace: flux-system
 spec:
   interval: 5m
-  targetNamespace: com-ermnvldmr
   sourceRef:
     kind: GitRepository
     name: ermnvldmr-repo