Update a candidate note. Fields that are omitted are left unchanged, and the acting user must be a Site Admin or the note's author. The endpoint follows the Greenhouse UI: body and visibility can be edited on NOTE, TOUCHPOINT and FEEDBACK notes, visibility can only switch between public and admin_only on a NOTE that is not private, and any other change returns 422. Greenhouse's own internal integrations can also edit other note types, subject, user_id and the email fields. Changing body clears body_with_tags and removes the note's @-mentions, since the API takes plain text; sending the current body changes nothing.