[FIX] website: enable animations when a cookie bar is displayed

Before this commit, when a cookie bar was displayed on a page and
elements of that page were animated (on scroll and on appearance), those
animations did not work while the cookie bar was present. This commit
fixes that and enables animations even if a cookie bar is displayed. The
problem was that we were looking to see if a modal (cookie bar, popup)
was displayed and if it was, all animations were based on the scroll
height of that modal. However, this should only be done for elements
that are in the modal. The other elements should always base their
animation on the scroll height of the page.

task-3151000

closes odoo/odoo#120294

Signed-off-by: Romain Derie (rde) <rde@odoo.com>