Link to upgrade instructions in Tails Installer when a Tails USB stick is selected
_Originally created by @emmapeel on [#7904 (Redmine)](https://public-redmine-archive.tails.boum.org/code/issues/7904)_
When opening the Tails installer, there is a documentation link pointing
to the installation assistant.
But this link doesn’t cover all options for the Tails installer, it just
talks about upgrading the USB stick with Clone & Install.
So, we should consider providing a link for the upgrade options (Manual
upgrade using Tails Installer).
Feature Branch: bugfix/7904-15590-14849-14720-14810-installer-fixes-for-3.9, kurono/installer:bug/7904-change-link-upgrade-instructions
### Related issues
- **Related to** tails/tails#5466
- **Related to** tails/tails#15392
issue