chore: remove README-helm3.md (#36561)
chore: remove README-helm3.md (#36561)

* chore: Update README with gateways in seperate ns

* chore: remove README-helm3.md

Out of date, please see https://istio.io/latest/docs/setup/install/helm/.
istio/istio,istio/istio,istio/istio,istio/istio,istio/istio