[Bug] Codecov CI step is silently failed from last week.

[filzrev]

Describe the bug

On GitHub Action CI.
It seems CodeCov step is silently failed from last week. (https://github.com/dotnet/docfx/actions/runs/8502861596)
with following warning.

test (ubuntu-latest)
Codecov: Failed to properly create commit: The process '/home/runner/work/_actions/codecov/codecov-action/v4/dist/codecov'
failed with exit code 1

Expected behavior

• Codecov step is successfully completed.
• CI error is reported as error if Codecov step is failed. (by enable additional fail_ci_if_error: true option)

[filzrev]

It seems failed because codecov/codecov-action@v4 drop supports for token-less uploads.
codecov/feedback#315

It need set to repository secret and explicitly specify CODECOV_TOKEN.
And set fail_ci_if_error: true to stop CI.

https://github.com/dotnet/docfx/blob/main/.github/workflows/ci.yml#L46-L47

    - uses: codecov/codecov-action@v4
      if: matrix.os == 'ubuntu-latest'
      with:
        fail_ci_if_error: true
        token: ${{ secrets.CODECOV_TOKEN }}