Use older checkout (#105)

Author: dduan

.github/workflows/deploy-docs.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v2
 
       - name: Make script executable
         run: chmod +x Scripts/generate-docs.sh