roachtest: apply more lenient permissions to private roachtest bucket

Currently, db engineers (particularly test-eng) cannot create or modify the storage buckets in the gce roachtest private project e2e-infra-381422, [here](https://console.cloud.google.com/storage/browser?forceOnBucketsSortingFiltering=true&project=e2e-infra-381422&supportedpurview=project&prefix=&forceOnObjectsSortingFiltering=false).

@Renato Costa and I would have liked to modify those buckets as part of [this PR](https://github.com/cockroachdb/cockroach/pull/110288#issuecomment-1719486942), but we were not able to.

To change the permissions on this project, some terraform changes are required [here](https://github.com/cockroachlabs/crl-infrastructure/tree/main/terraform/gcp/cockroachlabs.com/engineering/test-engineering/e2e-infra)

Jira issue: CRDB-31553