Update Src/Nager.Date/PublicHolidays/SouthKoreaProvider.cs
Update Src/Nager.Date/PublicHolidays/SouthKoreaProvider.cs

Co-authored-by: Tino Hager <4cb266776ab2e52e52d846404653efa684c7c176@nager.at>
tinohager/Nager.Date,tinohager/Nager.Date,tinohager/Nager.Date