Revised & translated the sources in instuments_ko.ts file to Korean

[lighteko]

I translated every sources in instruments_ko.ts file to Korean. There were several unnatural translations, so I fixed them as well.

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)

[Jojo-Schmitz]

Translations are done on Transifex, not via PRs