Rollback markdown to v3.2.0 (#492)

.github/workflows/mkdocs-build.yml

@@ -24,6 +24,7 @@ jobs:
       - name: Publish docs
         run: |
           pip install --upgrade pip && pip install setuptools mkdocs
+          pip install markdown==3.2.0
           python mkdocs/mkdocs-config/setup.py develop
           git config user.name 'github-actions[bot]' && git config user.email 'github-actions[bot]@users.noreply.github.com'
           cd mkdocs