[Tails-dev] [review'n'merge] update links

Hello, I made a branch to update some links in the website (and update
the Debian version in the Features page).

Please review and merge.

Repo: https://git-tails.immerda.ch/xin/tails/
Branch: update_links
Last Commit: b5172d11b4f7ac0f056c8430a8b7e6fcc29e3dcf

Cheers.
xin