chore(deps): update actions/download-artifact action to v6

Author: renovate[bot]

.github/workflows/update_assets.yml

@@ -29,7 +29,7 @@ jobs:
     needs: [ build ]
     steps:
       - name: Download build artefacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: assets
           path: assets/