Add group security settings API to nav

Add navigation item to global navigation

• Link to the merge request that introduced the new page: Add new API fo update secret push protection fo... (gitlab!175225 - merged)
• Give the MR a descriptive title.
• Optional. Link to the review app showing the new page: https://pw-add-group-security-api-nav.docs.gitlab-review.app/ee/api/group_security_settings.html