Fix an intermittent spec failure in spec/lib/gitlab/geo/database_tasks_spec.rb

What does this MR do?

Fixes an intermittent spec failure in spec/lib/gitlab/geo/database_tasks_spec.rb

Does this MR meet the acceptance criteria?

• [-] Changelog entry added, if necessary
• [-] Documentation created/updated
• [-] API support added
• [-] Tests added for this feature/bug
• Review
  • [-] Has been reviewed by UX
  • [-] Has been reviewed by Frontend
  • Has been reviewed by Backend
  • [-] Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

gitlab-org/gitlab-ee#3680