benchmark: update an obsolete path

PR-URL: https://github.com/nodejs/node/pull/12904
Refs: https://github.com/nodejs/node/issues/12903
Refs: https://github.com/nodejs/node/commit/ff001c1
Reviewed-By: Anna Henningsen <anna@addaleax.net>

benchmark/http/_chunky_http_client.js

@@ -3,7 +3,7 @@
 // test HTTP throughput in fragmented header case
 var common = require('../common.js');
 var net = require('net');
-var test = require('../../test/common.js');
+var test = require('../../test/common');
 
 var bench = common.createBenchmark(main, {
   len:  [1, 4, 8, 16, 32, 64, 128],