[FIX] website_forum: default karma

- Set the 'Editor Features: image and links' karma point to zero.
- Set a user with a total karma points < 30

The user doesn't see the links buttons in the editor.

This is because of an old fallback from 2014 which doesn't make sense
anymore today.

opw-2026025

closes odoo/odoo#34325

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>