Apply GitLab UI button styles to buttons in app/views/admin/users directory

Instructions

For instructions about how to apply GitLab UI button styles to the button instances on these templates, see the epic &4001 (closed).

Files in directory with buttons that needs migration

• app/views/admin/users/_form.html.haml
• app/views/admin/users/_head.html.haml
• app/views/admin/users/_user.html.haml
• app/views/admin/users/index.html.haml
• app/views/admin/users/projects.html.haml
• app/views/admin/users/show.html.haml