Update README.md

Author: pballai

plugin_use_cases/public/dashboard-builder/README.md

@@ -319,4 +319,4 @@ Message Types:
   - currentExploreKey: Active exploreKey for JWT generation
   - areaNodeIdMap: { "viz1_nodeid": "nodeId", ... }
   - availableBookmarks: Array of bookmark objects for dropdown
-  - currentBookmarkId: Currently loaded bookmark ID
+  - currentBookmarkId: Currently loaded bookmark ID