Fix OpenSearch operator installation command

Author: nilushancosta

docs/getting-started/production/multi-cluster.mdx

@@ -582,11 +582,13 @@ Clustered OpenSearch using the OpenSearch Operator for high availability.
 Install OpenSearch Operator:
 
 ```bash
-helm upgrade --install opensearch-operator \
-    oci://ghcr.io/opensearch-project/helm-charts/opensearch-operator \
+helm repo add opensearch-operator https://opensearch-project.github.io/opensearch-k8s-operator/
+helm repo update
+helm upgrade --install opensearch-operator opensearch-operator/opensearch-operator \
+    --create-namespace \
     --kube-context $OP_CONTEXT \
     --namespace openchoreo-observability-plane \
-    --create-namespace
+    --version 2.8.0
 ```
 
 Wait for the operator to be ready:

docs/getting-started/production/single-cluster.mdx

@@ -609,10 +609,12 @@ Clustered OpenSearch using the OpenSearch Operator for high availability.
 Install OpenSearch Operator:
 
 ```bash
-helm upgrade --install opensearch-operator \
-    oci://ghcr.io/opensearch-project/helm-charts/opensearch-operator \
+helm repo add opensearch-operator https://opensearch-project.github.io/opensearch-k8s-operator/
+helm repo update
+helm upgrade --install opensearch-operator opensearch-operator/opensearch-operator \
+    --create-namespace \
     --namespace openchoreo-observability-plane \
-    --create-namespace
+    --version 2.8.0
 ```
 
 Wait for the operator to be ready: