#31969 adds a net mainnet snapshot for v29

I generated a torrent for it. There was some discussion about whether we should put a binary seed on bitcoincore.org.

But that's just a performance detail. The main question is: should we link to the snapshot torrent from the release notes, installation instructions and/or the website?

We already commit to the hash in code, so it seems fine to me to link to a torrent - as long as enough people verify that its content matches.