[FIX] website_slides: avoid display error messages twice in quizz completion

Purpose of this commit is to avoid having error message replacing the
cross used to close the container of the error message.

Task ID 2058595
PR #36281

addons/website_slides/static/src/js/slides_course_quiz.js

@@ -95,7 +95,7 @@ odoo.define('website_slides.quiz', function (require) {
             } else if (alert_code === 'public_user') {
                 message = _t("You must be logged to submit the quiz.");
             }
-            this.$('.o_wslides_js_lesson_quiz_error span').html(message);
+            this.$('.o_wslides_js_lesson_quiz_error span:first').html(message);
             this.$('.o_wslides_js_lesson_quiz_error').removeClass('d-none');
         },