Remove --harmony-async-await runtime flag

test/mjsunit/es8/async-await-no-constructor.js

 // Copyright 2016 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-async-await --allow-natives-syntax
+// Flags: --allow-natives-syntax
 
 'use strict';
 
 var resolved = Promise.resolve();
 var count = 0;
 
 Object.defineProperty(Promise.prototype, 'constructor',
                       { get() { count++; return Promise; } })
 
 async function foo() {
   await resolved;
   return resolved;
 }
 
 async function bar() {
   throw 1;
 }
 
 foo();
 bar();
 %RunMicrotasks();
 assertEquals(1, count);