Update default values for combo macro

[s6t]

Set the default values as mentions in the official documentation (https://zmk.dev/docs/config/combos).

[urob]

Sorry for the slow response.

1/ The issue with explicitly setting the -1 default value is that Devicetree doesn't like negative integers. It's okay to leave them empty (and assign a negative default in the behavior definition). But explicitly setting negative integers via the dts results in an overflow.

Note that the current approach of setting a default of 0 for require-prior-idle-ms is functionally equivalent, as it always results in is_quick_tap being false:

https://github.com/zmkfirmware/zmk/blob/8a44ef109ae301ce084b32dd5fe25200da9e402f/app/src/combo.c#L159

2/ I don't have a strong opinion on the timeout default, but it would be a breaking change. So it's not clear to me that changing it provides enough of an upside.