fix(docs): replace version variable

Ref #5988

docs/modules/ROOT/pages/installation/installation.adoc

@@ -13,10 +13,11 @@ The first step is to install and run the Camel K operator. You can do it via any
 
 https://kustomize.io[Kustomize] provides a declarative approach to the configuration customization of a Camel-K installation. Kustomize works either with a standalone executable or as a built-in to `kubectl`. The https://github.com/apache/camel-k/tree/main/install[/install] directory provides a series of base and overlays configuration that you can use. You can create your own overlays or customize the one available in the repository to accommodate your need.
 
-```[subs=attributes+]
+[subs=attributes+]
+----
 $ kubectl create ns camel-k
 $ kubectl apply -k github.com/apache/camel-k/install/overlays/kubernetes/descoped?ref=v{last-released-version} --server-side
-```
+----
 
 You can specify as `ref` parameter the version you're willing to install (ie, `v{last-released-version}`). The command above will install a descoped (global) operator in the camel-k namespace. This is the suggested configuration in order to manage Integrations in all namespaces.