release_process: please clarify timestamp-related checks / please check 3.13 results

Originally created by @CyrilBrulebois on #16599 (Redmine)

(This ticket is a bit of a stretch, feel free to split it; bumping severity and setting target version to 3.14 to make sure it gets looked at in a timely fashion.)

Current post-release step:

1. Verify that the snapshots used in the release branch are ok,
   e.g. they use the correct snapshots, and they were bumped
   appropriately (they should expire after the major release _after_
   the one you're preparing). Look carefully at the output of this command:
[…]

First off: What is the “version you’re preparing”? Is it the version that was just published/released? Or one of the dummy versions that were added in various branches through debian/changelog?

Here’s the output I’ve saved for 3.13, please double check it:

config/APT_snapshots.d:
* Archive 'debian' uses snapshot '2019031601' which expires on: Sun, 01 Dec 2019 15:44:20 +0000
* Archive 'debian-security' uses snapshot 'latest' which expires on: never
* Archive 'torproject' uses snapshot '2019031301' which expires on: Thu, 28 Nov 2019 11:41:41 +0000
---
vagrant/definitions/tails-builder/config/APT_snapshots.d:
* Archive 'debian' uses snapshot '2019021901' which expires on: Fri, 08 Nov 2019 07:49:33 +0000
* Archive 'debian-security' uses snapshot '2019021901' which expires on: Fri, 08 Nov 2019 07:49:59 +0000
* Archive 'tails' uses snapshot '2019011801' which expires on: Fri, 08 Nov 2019 07:50:07 +0000
---