Extend XTKS hours to 15:30

[mzjp2]

Workflow to modify an existing Exchange Calendar

• Modify calendar class as required.
• Modify the test resources file (e.g tests/resources/{Exchange MIC}.csv), either manually or by executing python etc/make_exchange_calendar_test_csv.py {Exchange MIC}.
• Check if any of the fixtures in tests/test_{Exchange MIC}_calendar.py need updating to reflect your changes.
• Add references to any new/modified holidays in exchange_calendars/exchange_calendar_{Exchange MIC}.py.

Closes #432

See:

• https://www.jpx.co.jp/english/corporate/news/news-releases/1030/20230920-01.html
• https://www.jpx.co.jp/english/corporate/news/news-releases/1030/uorii50000002f2a-att/pressrelease_extension_of_trading_hours_en.pdf

I see that there is already an open PR to resolve this, but the tests are failing and it hasn't been merged: #429 so I've created this new one that is ready to be merged.

[mzjp2]

Can I also request that if this is merged, that we release a new version of the package relatively soon after so that everybody has the updated hours for XTKS ASAP given that this change is already live.

[gerrymanoim]

Thanks - will cut a new release when this lands.