Consider using the "manual" or "full" upgrade terminology in assistant

We’re currenly only talking about “upgrade” in https://tails.boum.org/upgrade/. This might be confusing as we also have automatic upgrades in Tails. Maybe we should say “manual upgrade” in both the router and overview.

Feature Branch: web/10735-say-manual-upgrade-in-assistant

Parent Task: #8590 (closed)

Original created by @sajolida on 10735 (Redmine)