fix(microservice) Delete unnecessary call of grpcClient.start

[youngkiu]

PR Checklist

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

(node:66623) DeprecationWarning: Calling start() is no longer necessary. It can be safely omitted.
    at ServerGrpc.start (<PATH>/node_modules/@nestjs/microservices/server/server-grpc.js:39:25)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async ServerGrpc.listen (<PATH>/node_modules/@nestjs/microservices/server/server-grpc.js:31:13)

The above warning message appeared, so even if I deleted this.grpcClient.start(); and ran it, it worked normally.

[kamilmysliwiec]

Could you please update unit tests?

[coveralls]

Pull Request Test Coverage Report for Build c45d97c3-4f7b-4739-b79c-0970a270f8df

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.001%) to 92.159%

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Files with Coverage Reduction	New Missed Lines	%
packages/microservices/server/server-grpc.ts	11	92.23%

Totals
Change from base Build 2bf2e4c8-5da9-4dd1-8f93-3b733029afc6:	-0.001%
Covered Lines:	6735
Relevant Lines:	7308

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💛 - Coveralls

[kamilmysliwiec]

LGTM

[kamilmysliwiec]

I'm going to temporarily revert this PR to avoid introducing a breaking change