Configuring outbound network access(docs/serving/outbound-network-access.md)

Is this topic still valid? During the knative.dev navigation restructure review this topic received the following comment:

"[matzew] This shouldn't be necessary any more, since we don't use Istio sidecars"

Please identify whether this topic is still accurate and should exist in the Knative docs. Or please open a PR with "fixes" or to otherwise delete the file.