Style of import project buttons were fixed in the new project page.

## What does this MR do?
I have fixed style of import project buttons in the new project page.

## Are there points in the code the reviewer needs to double check?
I don't think so.

## Why was this MR needed?
Because the buttons area hasn't looked well. Before this, it was scattered.

## What are the relevant issue numbers?
Fixes #19467 

## Screenshots (if relevant)
![Screen_Shot_2016-07-11_at_17.12.11](/uploads/35918f16b1b4d671ad33faf6caf530a2/Screen_Shot_2016-07-11_at_17.12.11.png)
![Screen_Shot_2016-07-11_at_17.11.24](/uploads/3030e1ecb7d109fbf4552987b4bfb242/Screen_Shot_2016-07-11_at_17.11.24.png)
![Screen_Shot_2016-07-11_at_17.11.50](/uploads/eb8ede86c256a2356b0210f3876c0143/Screen_Shot_2016-07-11_at_17.11.50.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) 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
- [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 !5183