Adding TOC

Author: SnehaGunda

articles/cosmos-db/TOC.yml

@@ -595,7 +595,7 @@
         items:
         - name: Elastic scale
           href: manage-scale-cassandra.md
-        - name: 
+        - name: Secondary indexing
           href: cassandra-secondary-index.md
       - name: How-to guides
         items: