update ref content toc

Author: mrbullwinkle

articles/cognitive-services/QnAMaker/toc.yml

@@ -145,8 +145,6 @@
       href: /rest/api/cognitiveservices/qnamaker4.0/alterations
     - name: QnA Maker 5.0 Preview 1
       href: /rest/api/cognitiveservices/qnamakerv5.0-preview.1/alterations
-    - name: QnA Maker 5.0 Preview 2
-      href: /rest/api/cognitiveservices-qnamaker/qnamaker5.0preview2/alterations
   - name: SDKs
     items:
     - name: C#