appendChoices for prompt doesn't support heroCard style

[guy-microsoft]

Looks like a breaking change from botbuilder:
Botbuilder:

        switch (style) {
            case ListStyle.inline:
                msg = ChoiceFactory.inline(choices, text, undefined, options);
                break;

            case ListStyle.list:
                msg = ChoiceFactory.list(choices, text, undefined, options);
                break;

            case ListStyle.suggestedAction:
                msg = ChoiceFactory.suggestedAction(choices, text);
                break;

            case ListStyle.heroCard:
                msg = ChoiceFactory.heroCard(choices as Choice[], text);
                break;

            case ListStyle.none:
                msg = MessageFactory.text(text);
                break;

            default:
                msg = ChoiceFactory.forChannel(channelId, choices, text, undefined, options);
                break;
        }

agents:

switch (style) {
            case ListStyle.inline:
                msg = choices_1.ChoiceFactory.inline(choices, text, undefined, options);
                break;
            case ListStyle.list:
                msg = choices_1.ChoiceFactory.list(choices, text, undefined, options);
                break;
            case ListStyle.none:
                msg = agents_hosting_1.MessageFactory.text(text);
                break;
            default:
                msg = choices_1.ChoiceFactory.forChannel(channelId, choices, text, undefined, options);
                break;
        }