Once we bump operator lib version to 0.27, domain mapping is included in spec.replicas as  https://github.com/knative/operator/commit/ba3e058a20893580a98a731080bd7b20433eaa6b

We should remove the setting from test yaml like:

https://github.com/openshift-knative/serverless-operator/blob/release-1.19/test/v1alpha1/resources/operator.knative.dev_v1alpha1_knativeserving_cr.yaml#L6-L8

https://github.com/openshift-knative/serverless-operator/blob/release-1.19/hack/lib/serverless.bash