Update Product Planning endpoint urgency

What does this MR do and why?

Updates urgency on additional Plan endpoints based on the same review of impact from !194132 (merged). This extends the urgency reduction to the PUT epic endpoint and epic notes endpoints that were not included in the original MR.

Urgency Lowered

These endpoints follow the same justification as the GET epic endpoints that were updated in !194132 (merged).

Caller ID	Previous Target	New Target	Why?
PUT /api/:version/groups/:id/(-/)epics/:epic_iid	1s	5s	Legacy Work Item REST API endpoints are not a priority, intended to be eclipsed by the GraphQL Work Items API. Consistent with the GET endpoint changes in !194132 (merged). A Working Group has been stood up to specifically address performance of the Work Items API as the priority. Main users are automations that run through the weekend and disproportionately spend error budget.
GET /api/:version/groups/:id/epics/:noteable_id/notes	1s	5s	Epic notes follow the same pattern as issue and merge request notes which are already low urgency. The impact for the user is low with a REST endpoint. Consistent with other notes endpoints that have low urgency.
PUT /api/:version/groups/:id/epics/:noteable_id/notes/:note_id	1s	5s	As above. Epic note updates should have the same urgency as other note operations which are already low urgency.

References

Related to !194132 (merged) - Update Plan API Urgencies

Screenshots or screen recordings

N/A - Backend API changes only

How to set up and validate locally

1. Verify the urgency changes are applied correctly by checking the route definitions
2. Test epic update operations and note operations to ensure they still function correctly
3. Monitor performance metrics to confirm the urgency changes take effect

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.