Microsoft.ContainerService (AKS) count should not have a default value if autoscaling is set

When using AKS with Virtual Machine Scale Sets (VMSS) and the cluster-autoscaler (https://docs.microsoft.com/en-us/azure/aks/cluster-autoscaler), there shouldn't be a default for the `count` argument of agent node pools as seen hereunder. Since manual scaling is forbidden in that context this is causing issues when making changes to a cluster. https://github.com/Azure/azure-rest-api-specs/blob/4322d98bc9f67a84b227ce9504983e84cc4893a6/specification/containerservice/resource-manager/Microsoft.ContainerService/stable/2019-08-01/managedClusters.json#L1349

Start with the agent node pool schema in specification/containerservice/resource-manager/Microsoft.ContainerService/stable/2019-08-01/managedClusters.json at the referenced count property, and review the linked AKS cluster-autoscaler documentation. Confirm how the count default conflicts with autoscaling, then validate that the schema no longer supplies that default for autoscaled pools.

Written by the indexing model from the issue text.