Provide CODECOV_TOKEN to codecov-action

[hackerwins]

What this PR does / why we need it:

Provide CODECOV_TOKEN to codecov-action

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

https://github.com/yorkie-team/yorkie-ios-sdk/actions/runs/8659763624/job/23746307969#step:8:31

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41.75%. Comparing base (29066e9) to head (aab0600).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #159   +/-   ##
=======================================
  Coverage   41.75%   41.75%           
=======================================
  Files         104      104           
  Lines       24721    24721           
=======================================
  Hits        10323    10323           
  Misses      14398    14398           

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