bump action

Author: thrasibule

.github/workflows/main.yml

@@ -62,7 +62,7 @@ jobs:
           sudo apt-get install pandoc texlive texlive-latex-extra dvipng
           make docs
 
-      - uses: actions/upload-artifact@v2
+      - uses: actions/upload-artifact@v4
         if: (matrix.python-version == '3.11') && (github.event_name == 'pull_request')
         with:
           name: "doc_${{ github.event.pull_request.number }}"