Can you try with the following:

clusterConfig = {
  "cluster_name": "cluster-name",
  "spark_version": "14.3.x-scala2.12",
  "node_type_id": "Standard_D14_v2",
  "azure_attributes": {
    "availability": "ON_DEMAND_AZURE"
  },
  "autoscale": {
    "min_workers": 5,
    "max_workers": 15
  }
}

I tested internally and worked for me, seems that you are using the job cluster creation mechanism to create an all purpose cluster.