Remove --harmony-async-await runtime flag

test/debugger/debug/harmony/debug-async-break-on-stack.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
-
-var Debug = debug.Debug;
-
-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() +
-        " to return a Promise, but it returned " + promise);
-  }
-
-  promise.then(function(value) { hadValue = true; actual = value; },
-               function(error) { hadError = true; actual = error; });
-
-  assertFalse(hadValue || hadError);
-
-  %RunMicrotasks();
-
-  if (hadError) throw actual;
-
-  assertTrue(
-      hadValue, "Expected '" + run.toString() + "' to produce a value");
-
-  assertEquals(expected, actual, msg);
-}
-
-var break_count = 0;
-var exception = null;
-
-function listener(event, exec_state, event_data, data) {
-  if (event != Debug.DebugEvent.Break) return;
-  try {
-    break_count++;
-    var line = exec_state.frame(0).sourceLineText();
-    print(line);
-    assertTrue(line.indexOf(`B${break_count}`) > 0);
-  } catch (e) {
-    exception = e;
-  }
-}
-
-
-async function g() {
-  setbreaks();
-  throw 1;  // B1
-}
-
-async function f() {
-  try {
-    await g();
-  } catch (e) {}
-  return 2;  // B2
-}
-
-function setbreaks() {
-  Debug.setListener(listener);
-  Debug.setBreakPoint(g, 2);
-  Debug.setBreakPoint(f, 4);
-}
-
-f();
-
-%RunMicrotasks();
-
-assertEqualsAsync(2, async () => break_count);
-assertEqualsAsync(null, async () => exception);
-
-Debug.setListener(null);