Merge branch 'remove-todo' into 'master'

Remove TODO for not documented stuff

We should not put a `TODO` in a released product.

See merge request !3553

doc/development/ui_guide.md

 # UI Guide for building GitLab 
 
-## Best practices for creating new pages in GitLab
-
-TODO: write some best practices when develop GitLab features.
-
 ## GitLab UI development kit
 
 We created a page inside GitLab where you can check commonly used html and css elements.