App Service Environments - Create Or Update DnsSuffix parameter is invalid

Documentation at https://docs.microsoft.com/en-us/rest/api/appservice/appserviceenvironments/createorupdate specifies I can supply the dnsSuffix parameter

dnsSuffix | string | No | DNS suffix of the App Service Environment.
-- | -- | -- | --

When trying to deploy an ASE using api version 2019-08-01 I get the following error: `DnsSuffix is invalid. For this api-version, DnsSuffix cannot be specified.`

I am deploying an ILB ASE usign an ARM template and this is the resource I have specified
```
{
"apiVersion": "2019-08-01",
"type": "Microsoft.Web/hostingEnvironments",
"name": "[parameters('aseName')]",
"kind": "ASEV2",
"location": "[parameters('location')]",
"zones": [
"[parameters('availabilityZone')]"
],
"properties": {
"name": "[parameters('aseName')]",
"location": "[parameters('location')]",
"ipSslAddressCount": 0,
"internalLoadBalancingMode": "3",
"dnsSuffix": "[parameters('dnsSuffix')]",
"virtualNetwork": {
"id": "[variables('vnetID')]",
"subnet": "[parameters('virtualNetworkSubnet')]"
}
}
}
```

Start by comparing the App Service Environment Create or Update documentation with the 2019-08-01 ARM template payload shown in the issue, focusing on the dnsSuffix property. Confirm whether the API behavior or the documented parameter is incorrect; done means the specification and documentation consistently describe whether dnsSuffix is supported.

Written by the indexing model from the issue text.