Add type and format specifiers on quantity property. (Azure#2489)

specification/commerce/resource-manager/Microsoft.Commerce/preview/2015-06-01-preview/commerce.json

@@ -180,6 +180,8 @@
           "description": "UTC end time for the usage bucket to which this usage aggregate belongs."
         },
         "quantity": {
+          "type": "number",
+          "format": "float",
           "description": "The amount of the resource consumption that occurred in this time frame."
         },
         "unit": {
@@ -489,4 +491,4 @@
       "description": "Client Api Version."
     }
   }
-}
+}