[FIX] website_slides: quiz success modal displayed properly

After refactoring the modal options to stop using the `Underscore.js`
library, the modal was not displayed properly anymore. You can check the
behavior by completing a quiz in the website_slides module.

If we set the `option` as the target of the `Object.assign()` we then
got the optiond properly applied and we got the same behavior as before.

Refactoring commit:
https://github.com/odoo/odoo/commit/f4f0f783183507df8227b37fe1234c256325df6d

opw-3389193

closes odoo/odoo#128132

X-original-commit: 46ed163e39238f7f4d7115711fe9dee93abd4cde
Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>

addons/website_slides/static/src/js/slides_course_quiz_finish.js

@@ -19,13 +19,13 @@ var SlideQuizFinishModal = Dialog.extend({
         this.quiz = options.quiz;
         this.hasNext = options.hasNext;
         this.userId = options.userId;
-        options = Object.assign({
+        options = Object.assign(options || {}, {
             size: 'medium',
             dialogClass: 'd-flex p-0',
             technical: false,
             renderHeader: false,
             renderFooter: false
-        }, options || {});
+        });
         this._super.apply(this, arguments);
         this.opened(function () {
             self._animateProgressBar();