Remove flakiness from EE promote issue to epic end-to-end test

What does this MR do?

Closes https://gitlab.com/gitlab-org/quality/nightly/issues/104#note_178031564.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content