[i18n-KO] Translated `main_classes/data_collator.md` to Korean (#33954)

* docs: ko: main_classes/data_collator.md

* feat: nmt draft

* fix: resolve suggestions

Co-authored-by: SeongWooChoi <46990061+nuatmochoi@users.noreply.github.com>

* fix: resolve suggestions

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Co-authored-by: SeongWooChoi <46990061+nuatmochoi@users.noreply.github.com>
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>