Update net-kourier nightly (#11539)
Update net-kourier nightly (#11539)

bumping knative.dev/net-kourier 0beb8c1...20428e9:
  > 20428e9 upgrade to latest dependencies (# 552)
  > 3593e87 upgrade to latest dependencies (# 551)

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