Update group security dashboard empty state section for unauthorized users

Problem to solve

The content (heading and paragraph) of the group security dashboard empty state added in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9517 could cause some confusion on whether something went wrong during load time. For example, see gitlab-org security dashboard as an anonymous user.

Intended users

This mostly affects Persona: Development Team Lead and Persona: Security Analyst.

Proposal

Approach A: Rephrasing the heading could suffice.

Approach B: Disabling access altogether and removing the menu item from the left sidebar could help.

Approach C: Alternatively, adding a signifier for unauthorized access could help in here and elsewhere.

What does success look like, and how can we measure that?

Making it clear that you are not authorized to view this could suffice.