Project export readiness review

Please review the following items in their entirety:

• sidekiq/index.md
• sidekiq/queue::project_export.md

Add suggestions/questions to the appropriate lines inside of this Merge Request in order for us to better address concerns and feedback. After you complete your review and all threads are resolved, please unassign yourself from this issue.

https://about.gitlab.com/handbook/engineering/infrastructure/production/readiness/#reviewing-a-proposal

Addresses: delivery#616 (closed)