Set docfx version

appveyor.yml

@@ -9,7 +9,7 @@ branches:
     - live
 
 install:
-  - cinst docfx
+  - cinst docfx --version 2.40.7
 
 build_script:
   - docfx
@@ -20,4 +20,4 @@ deploy_script:
   - git config --global user.email %GITHUB_EMAIL%
   - git config --global user.name "Blazor doc agent"
   - bash releaseDocs.sh
-  
+