Update amount.yml to fix data type (#327)

<!-- Ticket number or summary of work -->
Updated the type of the amount model to number and fixed description.
This is likely the reason that the Price theme object isn't rendering.

models/common/amount.yml

@@ -8,4 +8,5 @@ properties:
     type: string
     description: string representation of the price, including currency formatting
   value:
-    type: raw numeric value of the above price
+    type: number
+    description: numeric value of the price