Dequarantine epics management E2E spec

What does this MR do?

The MR dequarantines ee/browser_ui/2_plan/epic/epics_management_spec.rb - it was failing on Canary due to the Canary/Prod deployment problem. The code from !64524 (merged) was deployed to Canary but not to Production and the new NewEpicIssueWorker worker that was added in the MR was not working because of that. After the spec was quarantined and both Canary and Prod had the changes from !64524 (merged) the spec started to pass (https://ops.gitlab.net/gitlab-org/quality/canary/-/jobs/4222236#L3270).

E2E Test Failure issue(s)

• #334767 (closed)

Check-list

• General code guidelines check-list
  • Code review guidelines
  • Style guides
• Quarantine test check-list
  • Follow the Quarantining Tests guide.
  • Confirm the test has a quarantine: tag with the specified quarantine type.
  • Note if the test should be quarantined for a specific environment.
• Dequarantine test check-list
  • Follow the Dequarantining Tests guide.
  • Confirm the test consistently passes on the target GitLab environment(s).
    • (Optionally) Trigger a manual GitLab-QA pipeline against a specific GitLab environment using the RELEASE variable from the package-and-qa job of the current merge request.
• To ensure a faster turnaround, ask in the #quality Slack channel for someone to review and merge the merge request, rather than assigning it directly.