Inconsistent projects vs argoProjects key in values-standalone.yaml

## Description

The `values-standalone.yaml` uses `projects:` while `values-hub.yaml` uses `argoProjects:`. Should be consistent.

## Location

https://github.com/validatedpatterns/multicloud-gitops/blob/main/values-standalone.yaml#L10

```yaml
projects:
  - hub
  - config-demo
```

## Expected Behavior

Use `argoProjects:` to match values-hub.yaml.