manually install pandoc

Author: yanghan-microsoft

.github/workflows/gh-pages.yaml

@@ -20,10 +20,9 @@ jobs:
         python-version: '3.9'
 
     - name: Set up Pandoc
-      uses: docker://pandoc/core:2.9
-      # uses: actions/setup-pandoc@v1
-      # with:
-        # pandoc-version: 'latest' 
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y pandoc
 
     - name: Install dependencies
       run: |