Update net-istio nightly (#12975)
Update net-istio nightly (#12975)

bumping knative.dev/net-istio 5726ab2...9ab0b80:
  > 9ab0b80 upgrade to latest dependencies (# 931)

Signed-off-by: Knative Automation <f415700d4d0ce1c81810fe7553e3eea2bed16231@knative.team>
knative/serving,knative/serving