Install intel-microcode 3.20240312.1 to fix RFDS Intel CPU vulnerabilities

We install it from sid since it has not been released to stable
yet. This requires bumping Tails' Debian APT snapshot, which will
update a few other firmwares as well:

* firmware-linux-free  20200122-2 → 20200122-4
* firmware-sof-signed  2023.12-1  → 2023.12.1-1

Refs: tails/tails#20274