Merge pull request #223999 from bwren/toc1

Move WAF article to Overview

Author: 19BMG00

articles/azure-monitor/toc.yml

@@ -9,6 +9,8 @@ items:
     href: observability-data.md
   - name: What can you monitor?
     href: monitor-reference.md
+  - name: Optimize costs
+    href: best-practices-cost.md
   - name: What's new?
     href: whats-new.md
 - name: Concepts
@@ -1684,8 +1686,6 @@ items:
     items:
     - name: View and estimate charges
       href: usage-estimated-costs.md
-    - name: Optimize costs
-      href: best-practices-cost.md
     - name: Legacy Application Insights pricing
       href: app/legacy-pricing.md
     - name: Azure Monitor Pricing page