Align add button on repository view

## What does this MR do?
Top aligns the add button to the other UI elements adjacent to it 😄 

## Are there points in the code the reviewer needs to double check?
Shouldn't be

## Why was this MR needed?
Fixes a UI inconsistency 

## What are the relevant issue numbers?
Closes #21168 

## Screenshots (if relevant)
Before:
![Screen_Shot_2016-08-24_at_3.53.00_PM__2_](/uploads/5d6d765bb8a1d640170805ec32956790/Screen_Shot_2016-08-24_at_3.53.00_PM__2_.png)

After:
![Screen_Shot_2016-08-24_at_3.52.44_PM__2_](/uploads/1db9f0f68ef5defa4dd111d7dae1dc26/Screen_Shot_2016-08-24_at_3.52.44_PM__2_.png)

## 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 [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)

See merge request !5971