MSC1711 Upgrade FAQ should be removed from the docs sidebar

[anoadragon453]

This document isn't very relevant going forward. We probably don't need to keep it top-level.

The 1.0 UPGRADE notes already link to it. We should change that link to a github permalink and just remove it from the repo.

[richvdh]

honestly most of that doc can probably go away altogether.

[dklimpel]

This was fixed by

• Delete MSC1711_certificates_FAQ.md #11907