Modify documentation link in tails-installer UI to new installation assistant page

Originally created by @Anonymous on #13176 (Redmine)

Once #11576 (closed) has been done, tails-installer should point to the new page of the installation assistant. That is because people who run tails-installer won’t need the complete installation instructions, but only the second part of each installation, that is the creation of the “final Tails stick”.

Related issues

Blocked by #11576 (closed)

Edited May 15, 2020 by Anonymous

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information