docs: Update helm install commands (#350)

Author: xeniape

docs/modules/commons-operator/pages/installation.adoc

@@ -47,17 +47,14 @@ Helm::
 +
 --
 Helm allows you to download and deploy Stackable operators on Kubernetes.
-First ensure that you have installed the Stackable Operators Helm repository:
 
-[source,console]
-$ helm repo add stackable \
-  https://repo.stackable.tech/repository/helm-stable/
+NOTE: `helm repo` subcommands are not supported for OCI registries. The operators are installed directly, without adding the Helm Chart repository first.
 
-Then install the Stackable Commons Operator
+Install the Stackable Commons Operator
 
 [source,console]
 $ helm install --wait commons-operator \
-  stackable-stable/commons-operator --version 24.7.0
+  oci://oci.stackable.tech/sdp-charts/commons-operator --version 24.7.0
 
 Helm will deploy the operator in Kubernetes and apply the CRDs.
 --