.github: fix breaking change in download-artifact upgrade

Signed-off-by: Joachim Wiberg <[email protected]>

.github/workflows/container.yml

@@ -78,6 +78,7 @@ jobs:
         with:
           name: digests
           path: /tmp/digests
+          merge-multiple: true
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
       - name: Docker meta