test: remove TODO comment

The comment suggests adding randomness to the test suite.

PR-URL: #1820
Reviewed-By: Johan Bergström <[email protected]>

Author: Trott

test/parallel/test-preload.js

@@ -9,7 +9,6 @@ var nodeBinary = process.argv[0];
 var preloadOption = function(preloads) {
   var option = '';
   preloads.forEach(function(preload, index) {
-    // TODO: randomly pick -r or --require
     option += '-r ' + preload + ' ';
   });
   return option;