benchmark: remove querystring forced optimization

This removes all instances of %OptimizeFunctionOnNextCall from
querystring benchmarks

PR-URL: https://github.com/nodejs/node/pull/9615
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

benchmark/querystring/querystring-stringify.js

@@ -1,7 +1,6 @@
 'use strict';
 var common = require('../common.js');
 var querystring = require('querystring');
-var v8 = require('v8');
 
 var bench = common.createBenchmark(main, {
   type: ['noencode', 'encodemany', 'encodelast'],
@@ -36,10 +35,6 @@ function main(conf) {
   for (var name in inputs)
     querystring.stringify(inputs[name]);
 
-  v8.setFlagsFromString('--allow_natives_syntax');
-  eval('%OptimizeFunctionOnNextCall(querystring.stringify)');
-  querystring.stringify(input);
-
   bench.start();
   for (var i = 0; i < n; i += 1)
     querystring.stringify(input);