[BUG] gke-deploy does not update namespaces with new labels if the namespace already exists

## Notice

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## Affected builder image

gcr.io/cloud-builders/gke-deploy

## Expected Behavior

Applying an existing namespace with a new label will update the labels to what is in the YAML

## Actual Behavior

Applying an existing namespace with a new label does not update the namespaces labels at all.

## Steps to Reproduce the Problem

1. apply a namespace via a yaml file
```
---
apiVersion: v1
kind: Namespace
metadata:
name: dev
labels:
name: dev
role: shared-ingress
```
2. `kubectl get namespaces --show-labels` shows it has the above labels
3 update that namespace to add a new label
```
---
apiVersion: v1
kind: Namespace
metadata:
name: dev
labels:
name: dev
role: shared-ingress
pod-security.kubernetes.io/audit: restricted
```
4. `kubectl get namespaces --show-labels` shows the labels have not been updated

## Additional Info
doing these same steps but instead using kubectl locally they all work.