New York CTC maximum is too high

[nikhilwoodruff]

This isn't an actual problem in OpenFisca-US: the issue is that PolicyEngine 'flattens' the history into the current date (overwrites the last ten years and the next ten years with current policy). We don't need to do this, just for the next year, and here it causes an issue because the NY CTC explicitly depends on 2017 (pre-TCJA) parameter values.

[nikhilwoodruff]

Still seems to be an issue, investigating.