drop use of code-generator/generate-groups.sh #2502

Job	Run time
Unit Test (knative/serving)	10m 21s
Unit Test (knative/networking)	4m 40s
Unit Test (knative/eventing)	13m 13s
Unit Test (knative/operator)	7m 42s
Unit Test (knative/client)	7m 22s
Unit Test (knative-extensions/eventing-autoscaler-keda)	5m 8s
Unit Test (knative-extensions/eventing-ceph)	5m 14s
Unit Test (knative-extensions/eventing-github)	5m 48s
Unit Test (knative-extensions/eventing-gitlab)	5m 26s
Unit Test (knative-extensions/eventing-kafka-broker)	10m 5s
Unit Test (knative-extensions/eventing-rabbitmq)	8m 11s
Unit Test (knative-extensions/eventing-redis)	5m 48s
Unit Test (knative-extensions/kn-plugin-admin)	5m 26s
Unit Test (knative-extensions/net-certmanager)	4m 44s
Unit Test (knative-extensions/net-contour)	4m 53s
Unit Test (knative-extensions/net-istio)	5m 48s
Unit Test (knative-extensions/net-kourier)	5m 9s
	1h 54m 58s

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