Helm chart removes obsolete dedicated gateway configuration

The Helm chart no longer renders the obsolete dedicated per-account Kura gateway resources, including the --gateway-service-account-name controller flag. This keeps the Kura controller deployment healthy after the dedicated gateway feature was removed, because the flag was no longer recognized by the controller binary and would have caused the pod to crash-loop on startup. The chart also drops the related ServiceAccount, Roles, and ClusterRoleBindings that backed the dedicated gateway ingress controller.