Throttling info in DeleteByQueryResponse is optional (#2147)

Author: swallez

output/schema/schema.json

@@ -34,9 +34,9 @@ export class Response {
     slice_id?: integer
     task?: TaskId
     throttled?: Duration
-    throttled_millis: DurationValue<UnitMillis>
+    throttled_millis?: DurationValue<UnitMillis>
     throttled_until?: Duration
-    throttled_until_millis: DurationValue<UnitMillis>
+    throttled_until_millis?: DurationValue<UnitMillis>
     timed_out?: boolean
     took?: DurationValue<UnitMillis>
     total?: long