Update Azure armcontainerservice module to current

[mboersma]

The Azure backend to cluster-autoscaler is using an older version of the Azure SDK v2 package for armcontainerservice (AKS).

autoscaler/cluster-autoscaler/go.mod

Line 11 in b64817b

github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/containerservice/armcontainerservice/v5 v5.1.0-beta.2

We should update this to the currently supported API version (v8 right now), but there are breaking code changes.

[mboersma]

/area provider/azure
/area dependency
/kind cleanup

[mboersma]

/area cluster-autoscaler