Update TOC.yml

Author: ProfessorKendrick

articles/api-management/TOC.yml

@@ -215,6 +215,8 @@
       href: api-management-howto-autoscale.md
     - name: Plan and manage costs
       href: plan-manage-costs.md
+    - name: Service limits
+      href: service-limits.md
     - name: Use an external cache
       href: api-management-howto-cache-external.md
     - name: Configure update settings