Cloudformation template for Service Catalog cannot be deployed in other regions except us-east-1

In the Cloudformation template `drift-service-catalog.yaml`, the variable `${AWS::Region}` is used to dynamically change the URL of the CFN template for `BatchProduct` and `DeployProduct`. However, the original bucket `amazon-sagemaker-safe-deployment-pipeline` has only been deployed in `us-east-1`.

**Solution**:
Change line 218 and 235 to use only the template from region us-east-1 instead of a variable.

This has been tested and works. The template has to be updated not only in this GitHub repo, but also in the S3 bucket `amazon-sagemaker-safe-deployment-pipeline`, otherwise the "Launch stack" button will not work.