update ci

Author: gares

.github/workflows/main.yml

@@ -20,6 +20,7 @@ jobs:
         coq_version:
           - '8.20'
           - '9.0'
+          #- '9.1'
     steps:
     - uses: actions/checkout@v2
     - uses: coq-community/docker-coq-action@v1