gov.irs.deductions.itemized.salt_and_real_estate unit is null/None

[anth-volk]

I hope this isn't a trait of scale params, but for the param in the title, the unit in the metadata is null/None, making it difficult to properly parse when attempting to do some layout work on the front end. Would be great to modify -core to force parameters to have all of these properties and raise a build error if they don't.

[MaxGhenis]

It does have the unit:

policyengine-us/policyengine_us/parameters/gov/irs/deductions/itemized/salt_and_real_estate/cap.yaml

Line 3 in 0051378

unit: currency-USD

Might need propagate_metadata_to_children: true as I see it doesn't have $ in the web app.