azure-quickstart-templates/demos/cloud-shell-vnet/ is described being still on preview but which parts are on preview

[azure-quickstart-templates/demos/cloud-shell-vnet/](https://github.com/Azure/azure-quickstart-templates/blob/master/demos/cloud-shell-vnet/main.bicep#L184)

### Issue Details

Is `customDnsConfigs` property used on `first(first(privateEndpoint.properties.customDnsConfigs).ipAddresses)` to fetch IP address of private endpoint related nic on preview or GA?

It should be great to list used preview features in the README or in the template.

Currently given template is the only example setting A record IP to IP assigned for a private endpoint maybe there should be a smaller example without using other preview features.

### Repro steps (*if necessary, delete otherwise*)
1. Use similar code on west-europe deployment with identical API version
2. Notice that `SnowflakeprivatelinkEndpoint.properties.customDnsConfigs` returns empty array
3. Not suitable example for getting the IP address for a private endpoint

Start at demos/cloud-shell-vnet/main.bicep around line 184 and compare the customDnsConfigs usage with the API version and west-europe behavior described in the report. Document which features are preview or GA in the README or template, and verify whether the private-endpoint DNS lookup is suitable or a smaller example is needed.

Written by the indexing model from the issue text.