[Tails-l10n] Release schedule for Tails 5.12

Hi,

I'll be the Release Manager for Tails 5.12.

The current plan is:

- Mon, April 17: build 5.12 images, start testing
- Tue, April 18: finish testing, release

@developers: due to unavailability of core FT members during the
2 preceding weeks, code changes must be merged by Wednesday, April 5.
The only exception I already know we'll definitely need is the Tor
Browser upgrade (#19559). If you need other exceptions, please say so
as early as you can realistically anticipate.

@testers, please let me know how much time you'll have for manual QA
on:

- Mon, April 17: late afternoon, evening
- Tue, April 18: by 09:00 UTC

Cheers,
--
intrigeri