Fixed incorrect price amount formatting

no refs

- price amount formatting was incorrectly calling `toFixed` method on a string, which is not needed as we already round off the amount before formatting

ghost/admin/app/helpers/gh-price-amount.js

@@ -7,7 +7,7 @@ export function ghPriceAmount(amount) {
         if (price % 1 === 0) {
             return formatNumber(price);
         } else {
-            return formatNumber(Math.round(price * 100) / 100).toFixed(2);
+            return formatNumber(Math.round(price * 100) / 100);
         }
     }
     return 0;