message: Update modifyVisualization docs
diff: @@ -3429,6 +3429,9 @@ null;
  This message allows a client to modify the configuration for an existing
  visualisation.
  +A successful response means that the new visualization configuration has been
  +applied. In case of an error response, the visualization state does not change.
  +
  - **Type:** Request
  - **Direction:** Client -> Server
  - **Connection:** Protocol
  