throttle to one exec at a time

Author: parmentelat

.github/workflows/myst-to-pages.yml

@@ -64,7 +64,7 @@ jobs:
         run: |
           source venv/bin/activate
           cd notebooks
-          npx myst build --execute --html
+          npx myst build --execute --html --execute-parallel 1
       - name: Setup Pages
         uses: actions/configure-pages@v5
       - name: Upload artifact