Draft: Add troubleshooting direct transfer to navbar

Add navigation item to global navigation

• Link to the merge request that introduced the new page: gitlab!150607 (closed)
• Give the MR a descriptive title: gitlab!150607 (closed)
• Optional. Link to the review app showing the new page: https://main-ee-150607.docs.gitlab-review.app/ee/user/group/import/import_troubleshooting.html