Don't attach to window object

We don't want the store to be created if the labs flag is off

src/@types/global.d.ts

@@ -47,7 +47,6 @@ import { type DeepReadonly } from "./common";
 import type MatrixChat from "../components/structures/MatrixChat";
 import { type InitialCryptoSetupStore } from "../stores/InitialCryptoSetupStore";
 import { type ModuleApiType } from "../modules/Api.ts";
-import type RoomListStoreV3 from "../stores/room-list-v3/RoomListStoreV3.ts";
 
 /* eslint-disable @typescript-eslint/naming-convention */
 
@@ -100,7 +99,6 @@ declare global {
         mxToastStore: ToastStore;
         mxDeviceListener: DeviceListener;
         mxRoomListStore: RoomListStore;
-        mxRoomListStoreV3: RoomListStoreV3;
         mxRoomListLayoutStore: RoomListLayoutStore;
         mxPlatformPeg: PlatformPeg;
         mxIntegrationManagers: typeof IntegrationManagers;

src/stores/room-list-v3/RoomListStoreV3.ts

@@ -78,5 +78,3 @@ export default class RoomListStoreV3 {
         return this.internalInstance;
     }
 }
-
-window.mxRoomListStoreV3 = RoomListStoreV3.instance;