Adjust wording for canned ACLs to be clearer
Adjust wording for canned ACLs to be clearer

BrandonY/gsutil,dtjackson/gsutil,fishjord/gsutil,GoogleCloudPlatform/gsutil,ttiurani/gsutil,GoogleCloudPlatform/gsutil,craigcitro/gsutil,mattdr/gsutil,dimfeld/gsutil,chriskuehl/gsutil-debian