removed extaneous capitalization in TOC

Author: AbbyMSFT

articles/azure-monitor/toc.yml

@@ -579,7 +579,7 @@ items:
         href: ../service-health/alerts-activity-log-service-notifications-portal.md
     - name: Notifications and actions
       items:
-      - name: Alert Processing Rules
+      - name: Alert processing rules
         href: alerts/alerts-action-rules.md
         displayName: Azure CLI, az monitor action rule
       - name: Create action group