Merge branch 'ee-10539-variables-scss' into 'master'

EE: Removes EE differences for variables.scss

See merge request gitlab-org/gitlab-ee!10317

app/assets/stylesheets/framework/variables.scss

@@ -289,11 +289,9 @@ $gl-line-height: 16px;
 $gl-line-height-24: 24px;
 $gl-line-height-14: 14px;
 
-// EE-only CSS variables START
 $system-header-height: 35px;
 $issue-box-upcoming-bg: #8f8f8f;
 $pages-group-name-color: #4c4e54;
-// EE-only CSS variables END
 
 /*
 * Common component specific colors