Remove --harmony-async-await runtime flag

test/mjsunit/harmony/sloppy-no-duplicate-async.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
-
-// Async functions don't get sloppy-mode block-scoped function hoisting
-
-// No hoisting to the global scope
-
-{
-  async function foo() {}
-  assertEquals('function', typeof foo);
-}
-assertEquals('undefined', typeof foo);
-
-// No hoisting within a function scope
-(function() {
-  { async function bar() {} }
-  assertEquals('undefined', typeof bar);
-})();
-
-// Lexical shadowing allowed, no hoisting
-(function() {
-  var y;
-  async function x() { y = 1; }
-  { async function x() { y = 2; } }
-  x();
-  assertEquals(1, y);
-})();