Bump actions/upload-artifact from 3 to 4

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v3...v4)

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

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/main.yml

@@ -29,7 +29,7 @@ jobs:
         run: |
           python -m sphinx -W --keep-going --color -d _build/doctrees/ . _build/linkcheck/ -b linkcheck -q
       - name: Upload results
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         if: ${{ success() || failure() }}
         with:
           name: linkcheck