Delete Column

Permanently removes a specific column from an audience, including all cell values stored in that column across every row. Only columns where isDeletable is true can be removed using this endpoint; attempting to delete a non-deletable column returns 400. This action is irreversible — all data in the deleted column cannot be recovered. Returns 204 No Content on successful deletion. Returns 400 if the column is not deletable. Returns 404 if the audienceId or columnId does not exist.