feat: refactor after rebase

Author: vladislavkeblysh

src/index.scss

@@ -467,7 +467,6 @@
 @import "courseware/course/content-tools/contentTools.scss";
 @import "course-home/dates-tab/timeline/Day.scss";
 @import "course-home/outline-tab/Section.scss";
-@import "generic/upgrade-notification/UpgradeNotification.scss";
 @import "generic/upsell-bullets/UpsellBullets.scss";
 @import "course-home/outline-tab/widgets/ProctoringInfoPanel.scss";
 @import "course-home/outline-tab/widgets/FlagButton.scss";