Change recommendation of VM from using AV set to VMSS flexible

[infosatheesh2020]

We don't recommend customers to use AV sets for VMs not having AZ. The suggestion is to use VMSS Flexible instances.

https://azure.github.io/Azure-Proactive-Resiliency-Library-v2/azure-resources/Compute/virtualMachines/#migrate-vms-using-availability-sets-to-vmss-flex

https://learn.microsoft.com/en-us/azure/virtual-machines/availability-set-overview