always generate direct download links to dist.tpo

The links changed here all rely on a simple Apache2 rewrite which
redirects everything under www.tpo/dist/* to dist.tpo/*

Unless we do anything special with web log hits to this /dist/
subdirectory, we should point all the download links to dist.tpo
directly. The Android download links are already setup like that.

This would be a first step in fixing tpo/tpa/team#40667