Remove deprecated gRPC related comments

[seokho-son]

What would you like to be enhanced

• Code clean up for deprecated comments

Why is this needed

• To improve code readability and reduce the source file size.

Proposed solution

• Remove gPRC server related comments around https://github.com/cloud-barista/cb-tumblebug/blob/v0.9.14/src/main.go#L467C5-L467C33

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Additional note

• This is for a new contributor!

[ShehzadAhm]

Hi @seokho-son, can you assign it to me?