[FIX] website_forum: show votes from same forum

before this commit, if the user profile is opened
from a particular forum, the votes tab is displaying
the votes from all the forums for this user.

where us, the questions and answers tab is filtering
the data based on the selected forum.

after this commit, the data displayed in the votes
tab will also be filtered based on selected forum,
similar to questions and answers tab.

closes odoo/odoo#131431

X-original-commit: ae33d2e3
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>