Fix return type

Author: avstudnitz

lib/internal/Magento/Framework/Pricing/PriceCurrencyInterface.php

@@ -47,7 +47,7 @@ public function convertAndRound($amount, $scope = null, $currency = null, $preci
      * @param int $precision
      * @param null|string|bool|int|\Magento\Framework\App\ScopeInterface $scope
      * @param \Magento\Framework\Model\AbstractModel|string|null $currency
-     * @return float
+     * @return string
      */
     public function format(
         $amount,