remove livekit.livekit_service_url from sample config since SFU foci should be announced by homeserver's well-known

Author: fkwp

config/config.sample.json

@@ -5,9 +5,6 @@
       "server_name": "synapse.localhost"
     }
   },
-  "livekit": {
-    "livekit_service_url": "http://localhost:8080"
-  },
   "features": {
     "feature_use_device_session_member_events": true
   },