Changed CL Indigenous People's Day from fixed date june 21st to june solstice

[CrisBerriosL]

In the project there was a holiday specified for Chile as june 21st, when in reality it is for the winter solstice (southern hemisphere).
The holiday was approved in 2021, to be valid since 2022. In the year 2021, the holiday was set for june 21st in spite of that year's solstice falling on the 20th.

Made changes so the holiday is considered as june solstice in America/Santiago since 2022, and '06-21' for the year 2021.

Sources:

• This article is the law implemented in 2021 that indicates that the holiday for "Día Nacional de los Pueblos Indígenas" is on the winter solstice in the southern hemisphere, except that year where it is set to june 21st.
• This page has the chilean holidays for 2024 and 2025, in both cases the holiday is the 20th of june.