chore: update TUF spec version (#392)
chore: update TUF spec version (#392)

We fixed #321 but forgot to update this, so now the GH actions bot is
confused (#391).

Signed-off-by: Zachary Newman <395df8f7c51f007019cb30201c49e884b46b92fa@znewman.net>
theupdateframework/go-tuf