Update quickstart-deploy-application-gateway-for-containers-alb-controller.md

helm install in line 146 fails because of a mistake in $HELM_NAMESPACE. the command expects a namespace however the document instructs the user to insert the cluster name.  Fixed the mistake.

Author: msftnadavbh

articles/application-gateway/for-containers/quickstart-deploy-application-gateway-for-containers-alb-controller.md

@@ -142,7 +142,7 @@ You need to complete the following tasks before deploying Application Gateway fo
     ALB Controller can be installed by running the following commands:
 
     ```azurecli-interactive
-    HELM_NAMESPACE='<your cluster name>'
+    HELM_NAMESPACE='<namespace for deployment>'
     CONTROLLER_NAMESPACE='azure-alb-system'
     az aks get-credentials --resource-group $RESOURCE_GROUP --name $AKS_NAME
     helm install alb-controller oci://mcr.microsoft.com/application-lb/charts/alb-controller \