Change clusterSpec to chartRef in Redpanda spec for useFlux option

Author: RafalKorepta

modules/deploy/pages/deployment-option/self-hosted/kubernetes/k-deployment-overview.adoc

@@ -74,7 +74,7 @@ kind: Redpanda
 metadata:
   name: redpanda
 spec:
-  clusterSpec:
+  chartRef:
     useFlux: true  # or false, depending on your desired deployment mode
 ----