Fix CI and remove appveyor.yml (#610)

* Update net-ci-it.yml

* Delete appveyor.yml

Author: wu-sheng

.github/workflows/net-ci-it.yml

@@ -5,8 +5,7 @@ on:
     tags:
       - v*
     branches:
-      - develop
-      - master
+      - main
   pull_request:
 
 jobs: