fix broken reference (#436)

Author: adwk67

docs/modules/spark-k8s/pages/getting_started/installation.adoc

@@ -38,7 +38,9 @@ include::example$getting_started/getting_started.sh[tag=stackablectl-install-ope
 The tool will show
 
 [source]
-include::example$getting_started/code/install_output.txt[]
+----
+include::example$getting_started/install_output.txt[]
+----
 
 TIP: Consult the xref:management:stackablectl:quickstart.adoc[] to learn more about how to use stackablectl. For
 example, you can use the `--cluster kind` flag to create a Kubernetes cluster with link:https://kind.sigs.k8s.io/[kind].