Change "New Datalab User" button's endpoint

[avouacr]

The new user button on the homepage links to the admin doc of onyxia, and the link is broken anyway. It should point towards the user documentation instead, and be a region parameter because user documentations can differ depending on the instance. For now, it seems hardcoded in the UI :

onyxia/web/src/ui/pages/home/Home.tsx

Line 105 in ae775c0

href="https://docs.onyxia.sh/user-guide"