update azure cli setup (#337)

pages/reference/configuring-cloud-provider.md

@@ -111,6 +111,11 @@ Failure to do this could result in `project requested not found` or permission r
 
 - Follow the instructions [here](https://docs.microsoft.com/en-us/cli/azure/install-azure-cli) to install your Azure CLI.
 - Follow the instructions [here](https://docs.microsoft.com/en-us/cli/azure/get-started-with-azure-cli) to sign into your Azure CLI.
+- Install `aks-preview` extension for your Azure CLI:
+
+```
+az extension update -n aks-preview --allow-preview true
+```
 
 {% callout severity="warning" %}
 Keep in mind that your Azure subscription type can limit the availability of your VMs, so make sure to tailor your subscription