[PRQ#51038] Deletion Request for python-trading_calendars

MarsSeed [1] filed a deletion request for python-trading_calendars [2]: Discontinued since 2021 [a]; developer company Quantopian got shut down during that year. Not useful to keep. Upstream's readme recommends the usage of a newer alternative implementation, which is available on AUR: https://aur.archlinux.org/packages/python-pandas_market_calendars [a]: https://github.com/quantopian/trading_calendars [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/python-trading_calendars/