Make spatial audio Firefox-only

Hopefully explained in comment: we have a heisenbug where we sometimes
lack audio from a certain participant, so this simplifies the audio
path by removing the workaround required to do AEC with spatial audio
on chrome.

src/video-grid/VideoGrid.stories.tsx

@@ -21,8 +21,8 @@ import { RoomMember } from "matrix-js-sdk";
 import { VideoGrid, useVideoGridLayout } from "./VideoGrid";
 import { VideoTile } from "./VideoTile";
 import { Button } from "../button";
-import { TileDescriptor } from "../room/InCallView";
 import { ConnectionState } from "../room/useGroupCall";
+import { TileDescriptor } from "./TileDescriptor";
 
 export default {
   title: "VideoGrid",