Fix: [AzurePipelines] download Windows Dependencies from GitHub Releases

It turns out that Azure Pipelines has a lot of issues downloading
an artifact from your own project if it is triggered from a fork.
From what I could deduce, this is because the API requires a valid
token, which is not set (correctly?) when triggered from a fork.
As it is nicer anyway to publish the Windows Dependencies on GitHub,
it is now published there (and updated at least every week), and
we use the files from GitHub as our dependency.