Merge branch '24726-remove-across-gitlab' into 'master'

24726 Remove Across GitLab from side navigation

## What does this MR do?

Removes Across GitLab header from side navigation

## Screenshots (if relevant)
Before:
![Screen_Shot_2016-12-01_at_11.09.12_AM](/uploads/7a8c32a1736a55e0baedf071c21e98db/Screen_Shot_2016-12-01_at_11.09.12_AM.png)

After:
![Screen_Shot_2016-12-01_at_11.09.02_AM](/uploads/4d095ec6e4e756abf0301678bb40d59b/Screen_Shot_2016-12-01_at_11.09.02_AM.png)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) 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 #24726

See merge request !7883

app/assets/stylesheets/framework/gitlab-theme.scss

@@ -21,7 +21,6 @@
       background: $color-darker;
     }
 
-    .sidebar-header,
     .sidebar-action-buttons {
       color: $color-light;
       background-color: lighten($color-darker, 5%);

app/assets/stylesheets/framework/sidebar.scss

@@ -59,11 +59,6 @@
     padding: 0 !important;
   }
 
-  .sidebar-header {
-    padding: 11px 22px 12px;
-    font-size: 20px;
-  }
-
   li {
     &.separate-item {
       padding-top: 10px;

app/views/layouts/nav/_dashboard.html.haml

 .nav-sidebar
-  .sidebar-header Across GitLab
   %ul.nav
     = nav_link(path: ['root#index', 'projects#trending', 'projects#starred', 'dashboard/projects#index'], html_options: {class: "#{project_tab_class} home"}) do
       = link_to dashboard_projects_path, title: 'Projects', class: 'dashboard-shortcuts-projects' do

changelogs/unreleased/24726-remove-across-gitlab.yml

+---
+title: 24726 Remove Across GitLab from side navigation
+merge_request: 
+author: