Fix XML in ErrorResponse to have the correct name (#4)

See: rclone/rclone#7749

Co-authored-by: Nick Craig-Wood <[email protected]>

signature/signature-errors.go

@@ -19,6 +19,7 @@ type APIError struct {
 
 // the format of error response
 type errorResponse struct {
+	XMLName xml.Name `xml:"Error"`
 	Code    string
 	Message string
 }