l10n: update ko

무료 -> 자유 (ko) gratuit -> libre (fr)

It was written as "무료" which is translated to 'gratuit' in French. Since Korean language has a word "libre", let's use that instead.

• https://www.gnu.org/philosophy/free-sw.ko.html
• https://ko.wikipedia.org/wiki/%EC%9E%90%EC%9C%A0_%EC%86%8C%ED%94%84%ED%8A%B8%EC%9B%A8%EC%96%B4
• https://www.samsungsds.com/kr/insights/free-software.html "자유 소프트웨어(Free Software)는 무료 소프트웨어가 아닙니다!"