Update project security dashboard documentation

What does this MR do?

Affected doc page: https://docs.gitlab.com/ee/user/application_security/security_dashboard/#project-security-dashboard

This MR follows up on https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/13180

The project-level security dashboard has been updated and now looks like the group security dashboard. Thus, the screenshot in the documentation should be updated to reflect this change.

Does this MR meet the acceptance criteria?

Conformity

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