Refactor option_value_value_unit_scaled to use to_d instead of calling BigDecimal

As we are now using truncate(2) we don't need to specify the number of significant digits

app/services/variant_units/option_value_namer.rb

@@ -56,7 +56,7 @@ module VariantUnits
     def option_value_value_unit_scaled
       unit_scale, unit_name = scale_for_unit_value
 
-      value = BigDecimal(@variant.unit_value / unit_scale, 6).truncate(2)
+      value = (@variant.unit_value / unit_scale).to_d.truncate(2)
 
       [value, unit_name]
     end