clean formatMessage usage (facebook#9059)

Author: chenxsan

packages/react-dev-utils/formatWebpackMessages.js

@@ -106,12 +106,8 @@ function formatMessage(message) {
 }
 
 function formatWebpackMessages(json) {
-  const formattedErrors = json.errors.map(function (message) {
-    return formatMessage(message, true);
-  });
-  const formattedWarnings = json.warnings.map(function (message) {
-    return formatMessage(message, false);
-  });
+  const formattedErrors = json.errors.map(formatMessage);
+  const formattedWarnings = json.warnings.map(formatMessage);
   const result = { errors: formattedErrors, warnings: formattedWarnings };
   if (result.errors.some(isLikelyASyntaxError)) {
     // If there are any syntax errors, show just them.