Fix typo at youtube url link

courses_legacy/static/js/admin/new-course/controllers.js

             Course.get({id: $scope.course_id}, function(course){
                 if(course.intro_video) {
                     youtubePlayerApi.videoId = course.intro_video.youtube_id;
-                    $scope.link_video = `//www.youtube.com/embed/${course.intro_video.youtube_id}?rel=0&showinfo=0&autohide=1&theme=light&wmode=opaque`;
+                    $scope.link_video = "//www.youtube.com/embed/${course.intro_video.youtube_id}?rel=0&showinfo=0&autohide=1&theme=light&wmode=opaque";
                 }
                 document.title = 'Curso: {0}'.format(course.name);
                 $scope.addThumb = !course.thumbnail_url;