build(deps): Bump actions/upload-artifact from 4 to 6

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...v6)

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

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -211,7 +211,7 @@ jobs:
           tags: local/debuerreotype:latest
 
       - name: Upload debuerreotype image tarball
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: debuerreotype
           path: /tmp/debuerreotype.tar

.github/workflows/per-suite.yml

@@ -151,7 +151,7 @@ jobs:
                   --file - "${{ steps.debuerreotype.outputs.output_dir}}"
           docker run --rm "${tag}" apt-get update
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         if: ${{ steps.debuerreotype.outcome == 'success' }}
         with:
           name: ${{ env.CODENAME }}-${{ env.ARCH }}-rootfs