[CVE-2023-44487] Disable http2 for webhooks #2157

Job	Run time
Unit Test (knative/serving)	17m 53s
Unit Test (knative/networking)	9m 15s
Unit Test (knative/eventing)	21m 36s
Unit Test (knative/operator)	12m 21s
Unit Test (knative/client)	12m 4s
Unit Test (knative-extensions/eventing-autoscaler-keda)	8m 10s
Unit Test (knative-extensions/eventing-ceph)	7m 56s
Unit Test (knative-extensions/eventing-github)	8m 59s
Unit Test (knative-extensions/eventing-gitlab)	9m 14s
Unit Test (knative-extensions/eventing-kafka)	11m 9s
Unit Test (knative-extensions/eventing-kafka-broker)	15m 32s
Unit Test (knative-extensions/eventing-rabbitmq)	17m 31s
Unit Test (knative-extensions/eventing-redis)	10m 9s
Unit Test (knative-extensions/kn-plugin-admin)	9m 23s
Unit Test (knative-extensions/net-certmanager)	7m 31s
Unit Test (knative-extensions/net-contour)	7m 23s
Unit Test (knative-extensions/net-http01)	8m 32s
Unit Test (knative-extensions/net-istio)	9m 56s
Unit Test (knative-extensions/net-kourier)	7m 49s
	3h 32m 23s

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