Remove --harmony-async-await runtime flag

test/mjsunit/es8/async-arrow-lexical-this.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 assertEqualsAsync(expected, run, msg) {
   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 23 matching lines @@
 };
 
 assertEqualsAsync("1. PASS: [object LexicalThis]", () => O.run(1)("PASS"));
 
 var O2 = {
   [Symbol.toStringTag]: "LexicalThis",
   run: O.run(2)
 };
 
 assertEqualsAsync("2. PASS: [object LexicalThis]", () => O2.run("PASS"));