Retryable errors don't get retried in master

[jtackaberry]

isRetriableError() is broken in master which causes retryable errors to abort. Basically this function needs to look something like:

func isRetriableError(err error) bool {
	var apiErr smithy.APIError
	if !errors.As(err, &apiErr) {
		return false
	}
	switch apiErr.(type) {
	case *types.ExpiredIteratorException:
		return true
	case *types.ProvisionedThroughputExceededException:
		return true
	default:
		return false
	}
}

I can submit a PR but it's not entirely clear whether this project is dead or not, so I'll wait for signs of life before investing the effort. :)

[mskonovalov]

I guess this is fixed now in #159