Update bitcoin_ko_KR.ts

1. Fix some mistakes(typo, omission, spacing).
2. Re-adjust sentences to proper form.
3. Replace translation of certain words to better one.
4, Update legacy translations of upstream.
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I commit this first, and will commit another updates after 'translation resources' updates.

thanks.
Merge pull request #737 from nameEO/patch-1

Update bitcoin_ko_KR.ts