Remove usage of $.fadeIn from the codebase
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=214395) </details> <!--IssueSummary end--> The following discussion from !28509 should be addressed: - [ ] @kushalpandya started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/28509#note_321543093): (+4 comments) > And also, let's create a follow-up issue to remove usage of `$.fadeIn` from the codebase entirely (and link the created issue in a comment within the changes you've added).
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