Ensure U2F javascript runs on GroupSAML callback

What

Includes U2F javascript on Group::OmniauthCallbackController pages

Why

U2F was broken when signing in to GitLab.com using Group SAML. This was because the page dependant javascript wasn't included for that function

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/11796

Acceptance criteria

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Separation of EE specific content