Fix WidgetPip test having an incomplete mock (#32774)

* Fixup type

* no need to type this

* use createRef

apps/web/test/viewmodels/room/WidgetPip-test.ts

@@ -7,6 +7,7 @@
 
 import { type MatrixClient, type Room, RoomEvent } from "matrix-js-sdk/src/matrix";
 import { type MockedObject } from "jest-mock";
+import { createRef } from "react";
 
 import { mkRoom, stubClient } from "../../test-utils";
 import { WidgetPipViewModel } from "../../../src/viewmodels/room/WidgetPipViewModel";
@@ -50,6 +51,8 @@ describe("WidgetPipViewModel", () => {
         vm = new WidgetPipViewModel({
             room,
             widgetId,
+            onStartMoving: () => {},
+            movePersistedElement: createRef(),
         });
     });