build(deps): 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](https://github.com/actions/upload-artifact/compare/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>

.github/workflows/docs-upstream.yml

@@ -58,7 +58,7 @@ jobs:
           DOCS_FORMATS: yaml
       -
         name: Upload reference YAML docs
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: docs-yaml
           path: /tmp/buildx-docs/out/reference