drop toolchain directive #2272

Job	Run time
Unit Test (knative/serving)	9m 41s
Unit Test (knative/networking)	4m 15s
Unit Test (knative/eventing)	13m 30s
Unit Test (knative/operator)	7m 21s
Unit Test (knative/client)	3m 43s
Unit Test (knative-extensions/eventing-autoscaler-keda)	5m 36s
Unit Test (knative-extensions/eventing-ceph)	5m 6s
Unit Test (knative-extensions/eventing-github)	6m 9s
Unit Test (knative-extensions/eventing-gitlab)	5m 11s
Unit Test (knative-extensions/eventing-kafka)	7m 23s
Unit Test (knative-extensions/eventing-kafka-broker)	9m 51s
Unit Test (knative-extensions/eventing-rabbitmq)	11m 2s
Unit Test (knative-extensions/eventing-redis)	6m 20s
Unit Test (knative-extensions/kn-plugin-admin)	2m 38s
Unit Test (knative-extensions/net-certmanager)	4m 33s
Unit Test (knative-extensions/net-contour)	4m 53s
Unit Test (knative-extensions/net-http01)	4m 12s
Unit Test (knative-extensions/net-istio)	6m 28s
Unit Test (knative-extensions/net-kourier)	4m 43s
	2h 2m 35s

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