[FIX] website_slides: fix right panel alignment issue

There is an alignment issue while browsing courses page in Leaderboard and
Latest achievements panel.

In this commit we simply fix it with no-gutters to have all items aligned
properly.

TaskID - 2227683

closes odoo/odoo#49125

X-original-commit: 84270b8f542313235a35fc0449600a8ff5dc8785
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>