Update docker download url to use scarf gateway (#1523)
This updates the docker image download url to pass through the scarf
gateway, this allows anonymous tracking of downloads
Related to:
https://github.com/Unstructured-IO/unstructured#chart_with_upwards_trend-analytics
Testing:
docker pull
downloads.unstructured.io/unstructured-io/unstructured:latest
Result:
Image should download
