Release video rooms as a beta feature (#21962)

* Update labs documentation for the video rooms beta

* Make video rooms opt-out on develop

element.io/develop/config.json

@@ -59,7 +59,8 @@
         "apiHost": "https://posthog.element.io"
     },
     "features": {
-        "feature_spotlight": true
+        "feature_spotlight": true,
+        "feature_video_rooms": true
     },
     "map_style_url": "https://api.maptiler.com/maps/streets/style.json?key=fU3vlMsMn4Jb6dnEIFsx"
 }