Set cobra default output to stdout

[blurfx]

What this PR does / why we need it:

Fixes an issue that could not pipe output from the Yorkie CLI

Which issue(s) this PR fixes:

Fixes #490

Special notes for your reviewer:

cobra prints output to os.Stderr by default when calling the Print function internally. See https://github.com/spf13/cobra/blob/v1.7.0/command.go#L1349-L1351

So we can pipe the results if we explicitly tell it to output to Stdout like:

$ ./yorkie project ls --rpc-addr "api.yorkie.dev:443" | wc -l
2

$ ./yorkie project ls --rpc-addr "api.yorkie.dev:443" | awk 'NR>1 {print $1}'
myProject

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

• Added relevant tests or not required
• Didn't break anything

[codecov]

Codecov Report

Merging #599 (345f105) into main (7f39f2f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #599   +/-   ##
=======================================
  Coverage   51.45%   51.45%           
=======================================
  Files          66       66           
  Lines        6977     6977           
=======================================
  Hits         3590     3590           
  Misses       2911     2911           
  Partials      476      476           

[hackerwins]

Thanks for your contribution.