[FIX] eLearning, forum : tab visibility

From Website (Frontend) --> From the Courses --> From a course (with settings course : Course type = "Documentation" & Forum mentioned):
      The tab for the forum isn't there

From Website (Frontend) --> From the Courses --> From a course (with settings course : Course type = "Documentation" &  "Allow rating on Course" disabled):
      The tab for the review is always there

From Website (Frontend) --> From the Forum --> From a course (with settings course : Course type = "Documentation" & "Allow rating on Course" activivated):
     Click the tab for the review, the returned view is the course tab and not the review tab

From Website (Frontend) --> From the Forum  --> From a course (with settings course : "Allow rating on Course" disabled):
     The tab for the review is always there

closes odoo/odoo#37436

Task-id:  2074030
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>