Enable followRedirects in HttpManager.getNewHttpClient

The ability to host apk downloads from a different server than the index would be very useful for integrating with CDNs and overcoming the limits that free hosting plans place on file sizes. In my particular scenario, I need to serve the apk from a GitHub release, but even if I configure an index's mirror to reference https://github.com/org/rep/releases, their own download redirects to https://release-assets.githubusercontent.com/github-production-release-asset/SOME_OPAQUE_ID, so without the ability to follow HTTP redirects, the F-Droid client has no way to install the app.

Most (all?) client APIs automatically follow redirects by default. It needed to be explicitly disabled in the F-Droid client to block this from working, so this PR essentially just reverts to supporting standard and expected behavior.

I realize that this issue has been discussed before (#1164 (closed) and #1041 (closed)), and I understand the concerns around privacy and additional complexity. But OTOH, when a user chooses to trust the judgement of a repository they explicitly add, that trust extends to the decisions the repository maintainer makes about how and where to host the files.