[FIX] website: state not saved for accordion snippet

Before this commit, the states (collapsed/not collapsed) of the tabs
of the accordion snippet were not saved if it was the only changement
in edit mode.

After this commit, we trigger a content change when the states of the
tabs is changed.

task-2442237

closes odoo/odoo#67276

X-original-commit: 18af2ecade9482b5243059aefbfa79410ebf59a6
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>

addons/website/static/src/js/editor/snippets.options.js

@@ -1671,6 +1671,7 @@ options.registry.collapse = options.Class.extend({
         var self = this;
         this.$target.on('shown.bs.collapse hidden.bs.collapse', '[role="tabpanel"]', function () {
             self.trigger_up('cover_update');
+            self.$target.trigger('content_changed');
         });
         return this._super.apply(this, arguments);
     },