tests/resource/aws_autoscaling_group: Fix remaining S1039 reports
tests/resource/aws_autoscaling_group: Fix remaining S1039 reports

Previously:

```
$ make lint
aws/resource_aws_autoscaling_group_test.go:4353:9: S1039: unnecessary use of fmt.Sprintf (gosimple)
	return fmt.Sprintf(`
	       ^
aws/resource_aws_autoscaling_group_test.go:4393:9: S1039: unnecessary use of fmt.Sprintf (gosimple)
	return fmt.Sprintf(`
	       ^
aws/resource_aws_autoscaling_group_test.go:4437:9: S1039: unnecessary use of fmt.Sprintf (gosimple)
	return fmt.Sprintf(`
	       ^
aws/resource_aws_autoscaling_group_test.go:4518:9: S1039: unnecessary use of fmt.Sprintf (gosimple)
	return fmt.Sprintf(`
	       ^
make: *** [golangci-lint] Error 1
```

terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws