Commented out imagePullPolicy in hello-world-deployment.yaml

## Description

The `imagePullPolicy` is commented out, relying on Kubernetes defaults which may not be appropriate for all environments.

## Location

https://github.com/validatedpatterns/multicloud-gitops/blob/main/charts/all/hello-world/templates/hello-world-deployment.yaml#L28

```yaml
#imagePullPolicy: Always
```

## Expected Behavior

Set an explicit, templated imagePullPolicy.