[FIX] website: fix scrollButton option on events

On events, or in every part of the website that was built without
sections, the scroll button of a dropped snippet was not effective.

This was because we were targeting the next section, which was not there
in the previous case. Yet, we want it to scroll to the next element,
even if it is not a section.

task-2566338

closes odoo/odoo#72647

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>