⬆️ Bump actions/upload-artifact from 2 to 4

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 2 to 4.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v2...v4)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/publish.yml

@@ -69,7 +69,7 @@ jobs:
         run: |
           jb build lectures --path-output ./ --builder=custom --custom-builder=jupyter -n -W --keep-going
           zip -r download-notebooks.zip _build/jupyter
-      - uses: actions/upload-artifact@v2
+      - uses: actions/upload-artifact@v4
         with:
           name: download-notebooks
           path: download-notebooks.zip