301-servicebus-namespace-vnet doesn't match the docs it links to

[301-servicebus-namespace-vnet](https://github.com/Azure/azure-quickstart-templates/tree/master/301-servicebus-namespace-vnet)

### Issue Details
Readme points to docs at https://docs.microsoft.com/en-us/azure/service-bus-messaging/service-bus-service-endpoints, which show how to create firewall rules by creating a "Microsoft.ServiceBus/namespaces/networkruleset" resource. However the template creates a "Microsoft.ServiceBus/namespaces/VirtualNetworkRules" resource instead for the same purpose. This is confusing - what's the right approach?

Start by reviewing the 301-servicebus-namespace-vnet template and its README, then compare the linked Service Bus service endpoints documentation. Determine which resource approach is supported for the template, and update the template or documentation so they consistently describe the same configuration; verify the resulting template remains valid.

Written by the indexing model from the issue text.