deps: bump docker/build-push-action from 5 to 6

Pull-Request: libp2p#5473.

Author: dependabot[bot]

.github/workflows/docker-image.yml

@@ -30,7 +30,7 @@ jobs:
           images: ghcr.io/${{ github.repository }}-server
 
       - name: Build and push
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./misc/server/Dockerfile