The setting variable you're looking for is most likely
PREFECT_API_SERVICES_CANCELLATION_CLEANUP_ENABLED.
However, in the search results, I didn't locate this specific setting. It would be beneficial to check the
Prefect settings documentation for the most precise and updated details.
If you still have questions or if this variable is not documented, reaching out on Prefect's Slack or submitting an issue on GitHub might be the next step.