Merge branch 'ux-guide-link-update-contributing' into 'master'

Fix UX Guide link on Contributing.md

Current link on the CONTRIBUTING.md page was to the old UI Guide. This should be updated to the new link.

See merge request !7493

CONTRIBUTING.md

@@ -9,8 +9,6 @@
     - [Helping others](#helping-others)
     - [I want to contribute!](#i-want-to-contribute)
     - [Implement design & UI elements](#implement-design-ui-elements)
-        - [Design reference](#design-reference)
-        - [UI development kit](#ui-development-kit)
     - [Issue tracker](#issue-tracker)
         - [Feature proposals](#feature-proposals)
         - [Issue tracker guidelines](#issue-tracker-guidelines)
@@ -90,7 +88,7 @@ This was inspired by [an article by Kent C. Dodds][medium-up-for-grabs].
 
 ## Implement design & UI elements
 
-Please see the [UI Guide for building GitLab].
+Please see the [UX Guide for GitLab].
 
 ## Issue tracker
 
@@ -469,5 +467,5 @@ available at [http://contributor-covenant.org/version/1/1/0/](http://contributor
 [doc-styleguide]: doc/development/doc_styleguide.md "Documentation styleguide"
 [scss-styleguide]: doc/development/scss_styleguide.md "SCSS styleguide"
 [newlines-styleguide]: doc/development/newlines_styleguide.md "Newlines styleguide"
-[UI Guide for building GitLab]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/ui_guide.md
+[UX Guide for GitLab]: http://docs.gitlab.com/ce/development/ux_guide/
 [license-finder-doc]: doc/development/licensing.md