move models to be easier to find

Author: mrbullwinkle

articles/cognitive-services/openai/toc.yml

@@ -8,6 +8,8 @@ items:
       href: overview.md
     - name: Quotas and limits
       href: quotas-limits.md
+    - name: Models
+      href: ./concepts/models.md
     - name: Pricing
       href: https://azure.microsoft.com/pricing/details/cognitive-services/openai-service/
     - name: What's new
@@ -16,8 +18,6 @@ items:
   href: quickstart.md
 - name: Concepts
   items:
-    - name: Azure OpenAI models
-      href: ./concepts/models.md
     - name: Content filtering
       href: ./concepts/content-filter.md
     - name: Embeddings