webhooks.knative.dev/exclude is automatically added to webhooks

It seems that even when setting `webhook.namespaceSelector.matchExpressions` the following lines are still added to the Mutating and Admission Webhooks.
```
- key: webhooks.knative.dev/exclude
  operator: DoesNotExist
```

This causes issues in usages with products like argo-cd since its a constant drift.

It is also unclear why this exception is even added, and not managed using the chart.