change buildx version

Author: eedygreen

.github/workflows/deploy_testnet.yml

@@ -30,7 +30,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+        uses: docker/setup-buildx-action@v6
 
       - name: login to ghcr
         id: ghcr