Update Korean localization

[Canorus]

• Fix typo
• Change 'redo' translation to what majority agreed as the most natural one
• Add notification preference translation
• Add time format translation

[Canorus]

oh btw you might want to update all other translations as well. They didn't have time format either.

[h3poteto]

Yes, I hope that each language specialists will translate it.

[Canorus]

well wish there's some way to send notification, desirably automatically when translation file is changed, to whoever contributed in translation. I didn't even know there was new items to translate…

[Canorus]

I didn't have to close and pull a new request thanks to github, and github gracefully resolved the conversation as well.

[h3poteto]

No problem, thank you for your translation and fix.