Bump golang.org/x/sync from 0.8.0 to 0.9.0 #2468

Job	Run time
Unit Test (knative/serving)	9m 39s
Unit Test (knative/networking)	4m 5s
Unit Test (knative/eventing)	11m 51s
Unit Test (knative/operator)	6m 55s
Unit Test (knative/client)	6m 9s
Unit Test (knative-extensions/eventing-autoscaler-keda)	5m 1s
Unit Test (knative-extensions/eventing-ceph)	5m 14s
Unit Test (knative-extensions/eventing-github)	5m 36s
Unit Test (knative-extensions/eventing-gitlab)	5m 10s
Unit Test (knative-extensions/eventing-kafka-broker)	9m 1s
Unit Test (knative-extensions/eventing-rabbitmq)	8m 11s
Unit Test (knative-extensions/eventing-redis)	5m 18s
Unit Test (knative-extensions/kn-plugin-admin)	4m 56s
Unit Test (knative-extensions/net-certmanager)	4m 22s
Unit Test (knative-extensions/net-contour)	5m 4s
Unit Test (knative-extensions/net-istio)	5m 16s
Unit Test (knative-extensions/net-kourier)	4m 59s
	1h 46m 47s

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