[master] Update net-kourier nightly (#7876)
[master] Update net-kourier nightly (#7876)

Produced via:
  `curl https://storage.googleapis.com/knative-nightly/net-kourier/latest/$x > /workspace/source/./third_party/kourier-latest/$x`
/assign davidor markusthoemmes
/cc davidor markusthoemmes
/test pull-knative-serving-kourier-stable
knative/serving,knative/serving