Docs update for 4.1: installation

[eloquence]

We'll need to revise https://workstation.securedrop.org/en/stable/admin/install.html consistent with the install procedure on Qubes 4.1, including specific requests we have of our users to change any of the default settings (or to not change them, for that matter).

[sssoleileraaa]

One sub-task for this issue is for another team member who has a T490 (@zenmonkeykstop does, not sure about anyone else) to confirm the following issues (so that we know how to update our installation docs for those machines):

• Confirm this issue still occurs (it did for me)
• Confirm this issue occurs (follow my STR in the comment)

[zenmonkeykstop]

Also useful as the final push to get off my butt and do said upgrade...