[FIX] website: fix snippet animations not being destroyed before clone

In a80775ce, some code was refactored to stop using the confusing
'animation' denomination, as in reality they were just public facing
widgets that did many things, such as loading data based on
data-attributes and other things that were not always animation related.
One instance of the animation_stop_demand event was not renamed in the
_onSnippetWillBeCloned method, which creates some problems, one of which
being that the facebook snippet's iframe wouldn't be destroyed on clone,
but since the animation was started after the clone, this would result
in one facebook page snippet with two iframes with the facebook page,
for a total of 3 instead of 2, and one of these was unconfigurable.

This commit renames the event to restore the proper behavior.

closes odoo/odoo#42311

X-original-commit: 2a671f47f87e2bb52a5fade11ea6b79070516694
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>