Wait for requests in `edit_note` spec helper

What does this MR do?

As a follow up to !54227 (merged) and #321602 (closed), this MR uses wait_for_requests within the edit_note helper to reduce duplication and hopefully prevent flaky tests in future.

I also switched out wait_for_all_requests for wait_for_requests.

The former waits on rack requests as well as clientside ajax requests, but from local testing that didn't seem necessary (specs still passed)

Screenshots (strongly suggested)

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