change buildx version

Author: eedygreen

.github/workflows/deploy_testnet.yml

@@ -42,7 +42,7 @@ jobs:
 
       - name: build / tag / push docker image into ghcr
         id: build-and-push-tag
-        uses: docker/build-push-action@v3
+        uses: docker/build-push-action@v6
         with:
           context: .
           push: true