`updateCustomBenefit` does not update BenefitDetail on related Screener

## Bug
- Currently, updates to Custom Benefit fields such as `name` or `description` via `updateCustomBenefit(...)` do not also change the same fields on the corresponding `BenefitDetail`.

## Notes
- The purpose of having BenefitDetails on the Screener model is to allow us to get the name/descriptions of Custom Benefits related to a Screener quickly without having to individually query for each one. This allows the List page for Custom Benefits in a Screener to load more quickly than it otherwise would.
- It may be worth examining if there is a feature or strategy we can leverage to maintain this speed without having two sources of truth for fields like Custom Benefit name/description that need to be kept in-sync.