Bump actions/upload-artifact from 4 to 5

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 5.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...v5)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/docs-build.yml

@@ -45,7 +45,7 @@ jobs:
         run: |
           poetry run python -m sphinx -T -b html -d docs/_build/doctrees -D language=en docs docs/_build/html -n -W
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         name: Upload docs as artifact
         with:
           name: docs-html