Move GraphQL API navigation items for audit event streaming to Extend

What does this MR do and why?

After: gitlab!153397 (merged) (which adds a new page to the doc suite) and to contribute to gitlab#448616 (closed), make sure the new page is on the global nav, and that all related pages are on the nav in the right place.

Screenshots, screen recordings, or links to review app

Here is the new location of the pages on the navigation:

• https://eread-move-graphql-api-nav-items-for-audit-event-streaming-to-e.docs.gitlab-review.app/ee/administration/audit_event_streaming/graphql_api.html
• https://eread-move-graphql-api-nav-items-for-audit-event-streaming-to-e.docs.gitlab-review.app/ee/user/compliance/audit_event_streaming_graphql_api.html

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/doc/setup.md.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.