Remove --harmony-async-await runtime flag

test/mjsunit/es8/async-destructuring.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
 
 function assertThrowsAsync(run, errorType, message) {
   var actual;
   var hadValue = false;
   var hadError = false;
   var promise = run();
 
   if (typeof promise !== "object" || typeof promise.then !== "function") {
     throw new MjsUnitAssertionError(
         "Expected " + run.toString() +
@@ skipping 491 matching lines @@
    assertEquals(1, (async function(x, y = 1, z, v = 2, ...a) {}).length);
 })();
 
 (function TestDirectiveThrows() {
   "use strict";
 
   assertThrows("(async function(x=1){'use strict';})", SyntaxError);
   assertThrows("(async function(a, x=1){'use strict';})", SyntaxError);
   assertThrows("(async function({x}){'use strict';})", SyntaxError);
 })();