Merge branch '24017-long-build-list-dropdowns-which-scroll-are-not-immediately-obvious' into 'master'

change build list height to show 6,5 builds + improve padding of list, with firs…

## What does this MR do?

lets the builds dropdown in the pipeline graph show only 6,5 builds instead of 7.. so its easier to know if a user can scroll

## Are there points in the code the reviewer needs to double check?

I changed the padding of the list to 0 and gave the 8px top and bottom padding from the `ul` to the `first-child` and `last-child` li elements inside the list. Is that okey. Reason why, is that it breaks the list off correctly at the edges:)

![image](/uploads/f386e550a6044718035065a4ffd1e5a2/image.png) vs ![image](/uploads/4b535816f148771c26f4d4f3937d0305/image.png)




## Why was this MR needed?

easier to let people know when its possible to scroll.. to expect more builds

## Screenshots (if relevant)

![image](/uploads/ecfd34625063f566987a81f0e3f50251/image.png)


## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #24017

See merge request !7210