Ensure latest version of Azure Kubernetes Cluster is in use

Using older/un-patched versions of Azure Kubernetes Cluster may introduce a host of vulnerabilities.

In Azure Console -

1. Open the Azure Portal and go to Kubernetes Services.
2. Choose the cluster you wish to edit.
3. Under Settings, choose Cluster configuration.
4. For Kubernetes Version, select Upgrade version.

In Terraform -

1. In the azurerm_kubernetes_cluster resource, set kubernetes_version to the latest version.

References:
https://learn.microsoft.com/en-us/azure/aks/auto-upgrade-cluster
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/kubernetes_cluster#kubernetes_version