Delete cluster role to get, list, watch sources of eventing-contrib and knative-gcp in eventing repo

[capri-xiyue]

Problem
Delete cluster role to get, list, watch sources of eventing-contrib and knative-gcp in eventing repo.
In PR #1849, we added ClusterRole to get, list and watch sources of eventing-contrib and knative-gcp in config/200-source-resolvers-clusterrole.yaml.
This is a temporary solution. Such ClusterRole should eventually be moved to config directories in https://github.com/google/knative-gcp and https://github.com/google/eventing-contrib.
After google/knative-gcp#292 and knative/eventing-contrib#609 get merged, we should delete cluster role to get, list, watch sources of eventing-contrib and knative-gcp in eventing repo to avoid duplicate clusterrole

Exit Criteria
A measurable (binary) test that would indicate that the problem has been resolved.
Cluster role to get, list, watch sources of eventing-contrib and knative-gcp in eventing repo get deleted
Time Estimate (optional):
How many developer-days do you think this may take to resolve?
1-1
Additional context (optional)
Add any other context about the feature request here.

[grantr]

I think this was fixed by #2021. Please reopen if I'm wrong about that.