fs: remove duplicate check

Signed-off-by: Fedor Indutny <fedor@indutny.com>

Author: mscdex

lib/fs.js

@@ -944,7 +944,7 @@ fs.writeFile = function(path, data, options, callback) {
   assertEncoding(options.encoding);
 
   var flag = options.flag || 'w';
-  fs.open(path, options.flag || 'w', options.mode, function(openErr, fd) {
+  fs.open(path, flag, options.mode, function(openErr, fd) {
     if (openErr) {
       if (callback) callback(openErr);
     } else {