Decide what to do about HourCycle::H24

[sffc]

CLDR looks ready to deprecate it based on feedback from @hsivonen: https://unicode-org.atlassian.net/browse/CLDR-18303

We should decide what to do about it in the HourCycle enum for 2.0.

@zbraniecki @hsivonen

[zbraniecki]

Let's remove it.

[sffc]

Let's remove it.

What happens if someone hands us a locale with -u-hc-h24?

[zbraniecki]

We treat it as an invalid value and use the default for a given locale. I think that's the same as if the customer passed -u-hc-h25.

[sffc]

Does Locale --> Preferences conversion do this fallback (leaving None in place of unknown values)? If so I am totally onboard with this. I just would like to avoid throwing weird data-driven exceptions.

[sffc]

• @robertbastian We already support it and it is in UTS 35. So let's keep it
• @sffc It has no use cases, it is a big footgun, and CLDR plans to deprecate it. I think we should remove it now and @zbraniecki agrees.

Conclusion: 2.0-stretch, OK to remove.