[FIX] website: keep track of throttled scroll event target for Chrome

In Chrome, if a scroll event is not brand new, its `currentTarget` is
lost.

This commit makes sure that the `currentTarget` of the throttled scroll
event sent to `_onScrollWebsiteAnimate` is kept separately to avoid the
issue in case of throttling delay.

task-3449843

closes odoo/odoo#161850

X-original-commit: 277e9f292a031ed835f4135e597c17dab2fd067d
Signed-off-by: Benjamin Vray (bvr) <bvr@odoo.com>

addons/website/static/src/js/content/snippets.animation.js

@@ -1604,7 +1604,8 @@ registry.WebsiteAnimate = publicWidget.Widget.extend({
      * @param {Event} ev
      */
     _onScrollWebsiteAnimate(ev) {
-        this._scrollWebsiteAnimate(ev.currentTarget);
+        // Note: Do not rely on ev.currentTarget which might be lost by Chrome.
+        this._scrollWebsiteAnimate(this.$scrollingElement[0]);
     },
 });