fix some typos in CONTRIBUTING-ko.md

[fidemin]

What does this PR do?

• English: fixes some typos in CONTRIBUTING-ko.md
• 한글: CONTRIBUTING-ko.md에 있는 몇가지 오탈자를 수정하였습니다.

For resources

Description

Why is this valuable (or not)?

How do we know it's really free?

For book lists, is it a book? For course lists, is it a course? etc.

Checklist:

• Read our contributing guidelines
• Search for duplicates.
• Include author(s) and platform where appropriate.
• Put lists in alphabetical order, correct spacing.
• Add needed indications (PDF, access notes, under construction)

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!

[LuigiImVector]

To tick the checklist you must write: [X] Read our contributing... (X with no whitespaces aroud)

[eshellman]

Thanks, and welcome to free-programming-books!

[fidemin]

@LuigiImVector Thank you. I corrected it!