[Enhancement] update the NamingExample in Nacos 2.x

[brotherlu-xcq]

Describe the bug

nacos/example/src/main/java/com/alibaba/nacos/example/NamingExample.java

Line 52 in d929c2e

naming.registerInstance("nacos.test.3", "2.2.2.2", 9999, "DEFAULT");

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

[realJackSun]

@i will solve it@

[realJackSun]

This can truely confuse the users

[brotherlu-xcq]

Hi, @JackSun-Developer . How about this issue? if you have no time to do it, I think you can assign it to me. I will try to fix it.

[realJackSun]

@brotherlu-xcq thanks