build(deps): bump actions/download-artifact from 5 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/validate-upstream.yml

@@ -39,7 +39,7 @@ jobs:
           repository: docker/docs
       -
         name: Download data files
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         if: ${{ inputs.data-files-id != '' && inputs.data-files-folder != '' }}
         with:
           name: ${{ inputs.data-files-id }}