Remove runtime flags for Proxy and Reflect

test/mjsunit/es6/proxies-object-assign.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-proxies
-
 var handler = {
   ownKeys: function(t) { return ["a", "b"]; },
   getOwnPropertyDescriptor: function(t, p) {
     return {enumerable: true, configurable: true}
   },
   get: function(t, p) {
     return 1;
   }
 };
 
 var proxy = new Proxy({}, handler);
 
 var o = {};
 
 Object.assign(o, proxy);
 
 assertEquals({"a": 1, "b": 1}, o);
 
 (function TestStringSources() {
   var source = "abc";
   var target = {};
   Object.assign(target, source);
   assertEquals({0: "a", 1: "b", 2: "c"}, target);
 })();