Update articles/cosmos-db/mongodb/TOC.yml

Fixed capitalization per Microsoft style guide.

Author: v-dirichards

articles/cosmos-db/mongodb/TOC.yml

@@ -246,7 +246,7 @@
           href: ../data-residency.md?toc=/azure/cosmos-db/mongodb/toc.json
     - name: Automatic recommendations
       href: ../automated-recommendations.md?toc=/azure/cosmos-db/mongodb/toc.json
-    - name: Change Log
+    - name: Change log
       href: change-log.md
     - name: API version 4.2
       href: feature-support-42.md