Update net-istio nightly (#11808)
Update net-istio nightly (#11808)

bumping knative.dev/net-istio 4a4ace3...a9ab562:
  > a9ab562 Update community files (# 720)

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