Add hover to trash icon in notes

## What does this MR do?

Adds hover to trash icon in notes (fixes a ~regression).

## Screenshots (if relevant)

### Before
![Peek_2016-10-20_16-02](/uploads/5b7b94e0a0a3cd7c33d60084ff364f42/Peek_2016-10-20_16-02.gif)

### After
![Peek_2016-10-20_16-01](/uploads/b365eea616efdb7de98900e2925a4813/Peek_2016-10-20_16-01.gif)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [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 it does - 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 #23487

See merge request !7008