fix(chart): add missing namespace to webhook.ingress

[maigl]

I think I found a small bug:
When deploying the helm chart with:

helm template --namespace 'my-runner-namespace' ... | kubectl apply -f -

the ingress of the webhook server is deployed into namespace default instead
of my-runner-namespace. All other resources seem to be deployed into the correct namespace.

proposed fix:
The ingress needs to be deployed in the very same namespace as the service it is forwarding to.

_{Michael Kuhnt michael.kuhnt@mercedes-benz.com Mercedes-Benz Tech Innovation GmbH (ProviderInformation)}

[mumoshu]

LGTM. Thanks a lot for fixing it!