app

Fix page scrolling to top on sidebar toggle

## What does this MR do?

Prevents page from scrolling to the top when a user clicks sidebar closing hamburger icon as well as when a user is toggling sidebar pinning.

## Why was this MR needed?

When a user is closing the sidebar or pinning the sidebar the scroll position of the page should not be affected.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Closes #22851

See merge request !6627