cloud/storage/drive: update Delete op

Change-Id: I50c7505e277aee971ff5ff3905535259e5c71451
Reviewed-on: https://upspin-review.googlesource.com/18860
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/cloud/storage/drive/drive.go b/cloud/storage/drive/drive.go
index ffecbca..9abdd8b 100644
--- a/cloud/storage/drive/drive.go
+++ b/cloud/storage/drive/drive.go
@@ -139,7 +139,7 @@
 }
 
 func (d *driveImpl) Delete(ref string) error {
-	const op = "cloud/storage/drive.Download"
+	const op = "cloud/storage/drive.Delete"
 	id, err := d.fileId(ref)
 	if os.IsNotExist(err) {
 		// nothing to delete