Coronation of King Charles III not included in UK bank holidays

[gmyrianthous]

Even though the PR that adds the coronation to the UK calendar for 2023 was merged earlier this year, this doesn't seem to work:

>>> from workalendar.europe import UnitedKingdom
>>> from datetime import date
>>> 
>>> cal = UnitedKingdom()
>>> cal.holidays(2023)
[(datetime.date(2023, 1, 1), 'New year'), (datetime.date(2023, 1, 2), 'New Year shift'), (datetime.date(2023, 4, 7), 'Good Friday'), (datetime.date(2023, 4, 9), 'Easter Sunday'), (datetime.date(2023, 4, 10), 'Easter Monday'), (datetime.date(2023, 5, 1), 'Early May Bank Holiday'), (datetime.date(2023, 5, 29), 'Spring Bank Holiday'), (datetime.date(2023, 8, 28), 'Late Summer Bank Holiday'), (datetime.date(2023, 12, 25), 'Christmas Day'), (datetime.date(2023, 12, 26), 'Boxing Day')]
>>> 
>>> cal.is_working_day(date(2023, 5, 8))
True
>>> cal.is_holiday(date(2023, 5, 8))
False
>>> workalendar.__version__
'17.0.0'

[adamchainz]

Is this due to the 17.0.0 release not including that change? See #746