docs: document onTrafficUpdated listener as Android only (googlemaps#289

)

src/navigation/navigation/types.ts

@@ -177,7 +177,7 @@ export interface NavigationCallbacks {
   onReroutingRequestedByOffRoute?(): void;
 
   /**
-   * Callback function invoked when traffic data is updated.
+   * Callback function invoked when traffic data is updated (Android only).
    */
   onTrafficUpdated?(): void;