docs(microservices): Update ip address:port for a gRPC Docker server

[youngkiu]

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What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
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What is the current behavior?

Issue Number: N/A

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Does this PR introduce a breaking change?

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• No

Other information

Actually
https://github.com/youngkiu/nest/blob/7f00840c074ba5a5f233f73ef6c8456115abd7c1/packages/microservices/constants.ts#L11, I wanted to suggest modifying GRPC_DEFAULT_URL,
Since it was clearly stated as Default in the document, I thought there was an intention to do this.

So, I suggest modifying the example in the document.
In the case of servers, it is often built and used as a docker image.
0.0.0.0:50051 seems more appropriate as an example than localhost:50051.

In particular, in the case of gRPC in the target group of the AWS load balancer,
since the success code of the health check is 12(UNIMPLEMENTED),
I hope that if the example is 0.0.0.0:50051 it will further reduce confusion.

[kamilmysliwiec]

lgtm