How do I hide a radio button's "No value selected" in the Admin UI when we using DataDrivenEnumeration?

Take for example the  taxCode field in in SkuImp.

@Column(name = "TAX_CODE")
@AdminPresentation(friendlyName = "SkuImpl_Sku_TaxCode", order = 1001, group = GroupName.Financial)
@AdminPresentationDataDrivenEnumeration(optionCanEditValues = true, optionHideIfEmpty = true, optionFilterParams = { @OptionFilterParam(
            param = "type.key", value = "TAX_CODE", paramType = OptionFilterParamType.STRING) })
protected String taxCode;

The "No value selected" radio shows up for DataDrivenEnumeration when the field is NOT required or if it doesn't have a defaultValue set. You can use metadata overrides to set a default value for this field or make it required. This is driven by BasicFieldMetadata#getAllowNoValueEnumOption().

Alternatively, you could set the following property which will cause all DataDrivenEnumeration fields to render as drop-downs.