Fix the manifest file to specify the urls where dataapibuilder will be available upon release

[Aniruddh25]

Today, the manifest file dab-manifest.json that is created as part of the release points to github release zip urls. But we have not open sourced yet, so these urls wouldn't work. This issue is to replace them with the correct urls - that of the CDN pointing to the artifacts where we will host DAB - based on #886.

Once we open source, the urls need to be changed again to be the github release links.