Apply GitLab UI button styles to buttons in app/views/admin/groups 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/groups/_form.html.haml
• app/views/admin/groups/_group.html.haml
• app/views/admin/groups/index.html.haml
• app/views/admin/groups/show.html.haml