Fix merge_request_spec test

In merge_request_spec.js one of the async tests is not properly wrapped into setTimeout, failing when being run separately

See #67206 (moved) for details

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• [-] 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