'gsutil cp' requires storage.objects.list permission on source bucket

(see https://github.com/GoogleCloudPlatform/gsutil/issues/546 for a similar issue)

I think either the documentation went out of date again or there was a regression in gsutil. this command
```
gsutil cp gs://hadoop-lib/bigquery/bigquery-connector-hadoop3-0.19.1.jar .
```
fails with
```
AccessDeniedException: 403 @.com does not have storage.objects.list access to the Google Cloud Storage bucket.
```
I think only google employees should have ls permissions on gs://hadoop-lib. the documentation says that storage.objects.list is only required on the destination bucket, and that does not appear to be the case - anymore, at least.

Start by reproducing the listed `gsutil cp` command and compare its permission requirements with the documentation referenced in the issue. Determine whether the source-bucket listing requirement is a regression or a documentation mismatch; done means the behavior and documented permissions agree, with the relevant fix verified.

Written by the indexing model from the issue text.