[ci] Update actions/download-artifact action to v6

Author: lpinca

.github/workflows/ci.yml

@@ -81,7 +81,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           path: prebuilds
       - run: echo "version=$(git describe --tags)" >> $GITHUB_OUTPUT