fix(HU,#464): update the name of the public holiday on March 15

[humenmar]

Hello,

this PR should resolve this issue https://github.com/commenthol/date-holidays/issues/464.

Info sources:

• https://studyinhungary.hu/living-in-hungary/menu/national-holidays.html
• https://en.wikipedia.org/wiki/Public_holidays_in_Hungary
• https://publicholidays.hu/revolution-day/

[commenthol]

@humenmar Thanks