Testnet snapshot instructions are no longer valid

[BrandtH22]

Throughout the docs there are a few instances of testnet snapshot instructions that are deprecated. Previously we provided a full DB available for direct download but now one must use the torrent.

Once we have the fixed torrents out tomorrow I will be testing a symlink created for the torrent file and new commands that will enable a headless db snapshot setup similar to that which was used previously with the complete db snapshot

[BrandtH22]

The docs update to resolve this issue is in testing here:
#783