Fix promote issue to epic spec

What does this MR do?

Fixes a transient failure in the promote issue to epic spec by waiting until the epics list displays the new epic. If the test does fail, now screenshots will show where the actual failure is as well.

Closes #35880 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content