Expert Linux install instructions should mention apt update before installing debian-keyring
Originally created by @emmapeel on #12524 (Redmine)
A user got stuck on our website install instructions for
https://tails.boum.org/install/expert/usb/index.en.html
because an apt-get update was needed before installing the debian-keyring package.
Maybe we can add a `sudo apt update` before `sudo apt install debian-keyring`?
I can do it if people agrees…