Refactor: Aid to health time series chart

[jm-rivera]

Refactor aid to health time series chart. This and other charts rely on a function called id_to_sectors_ts, which must be refactored first, as covered in #53.

Refactoring the function here will involve filtering the right "health" sectors. You can continue to use the .filter_health_sectors function but check if there are any required improvements.

From there, you shouldn't need to change much.

https://github.com/ONEcampaign/aftershocks_data/blob/fb49e2558e727b3712935c0fd96e12c343415627/scripts/oda/overview_charts.py#LL218-L240