storage: fix reference to CopyFrom in doc comment
@@ -42,7 +42,7 @@ type Copier struct {
RewriteToken string
// ProgressFunc can be used to monitor the progress of a multi-RPC copy
- // operation. If ProgressFunc is not nil and CopyFrom requires multiple
+ // operation. If ProgressFunc is not nil and copying requires multiple
// calls to the underlying service (see
// https://cloud.google.com/storage/docs/json_api/v1/objects/rewrite), then
// ProgressFunc will be invoked after each call with the number of bytes of
