fix(instances): fix YAML indentation in code block (#3747)

Author: NoSuchCommand

compute/instances/troubleshooting/fix-dns-routed-ipv6-only-debian-bullseye.mdx

@@ -114,7 +114,7 @@ If your Instance is affected by the DNS resolution issue, follow the procedure b
     ```sh
     > /etc/cloud/cloud.cfg.d/99_scw_ip6dns.cfg cat <<EOF
     system_info:
-    network:
+      network:
         renderers: [netplan, eni]
         activators: [netplan, eni]
     EOF