Describe the bug

update the NamingExample in Nacos 2.x, as we know, Nacos 2.x use grpc connection to bind Client with Server, one Client can only register one Instance. So I think we can update the NamingExample, or else it will confuse the user.

Expected behavior
update the NamingExample

Acutally behavior

How to Reproduce
Steps to reproduce the behavior:
run the NamingExample, you will get no instanse.

Desktop (please complete the following information):

• OS: [e.g. Centos]
• Version [2.0.1]
• Module [example]

Additional context
no