Remove --harmony-async-await runtime flag

test/debugger/debug/harmony/async-debug-basic.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
-
-Debug = debug.Debug
-
-listenerComplete = false;
-breakPointCount = 0;
-
-async function f() {
-  await (async function() { var a = "a"; await 1; debugger; })();
-
-  var b = "b";
-
-  assertTrue(listenerDone);
-  assertFalse(exception);
-  assertEquals(1, breakpointCount);
-}
-
-function listener(event, exec_state, event_data, data) {
-  try {
-    if (event != Debug.DebugEvent.Break) return;
-
-    breakpointCount++;
-    listenerDone = true;
-    assertEquals("a", exec_state.frame(0).evaluate("a"));
-    assertEquals("b", exec_state.frame(1).evaluate("b"));
-    assertEquals("c", exec_state.frame(2).evaluate("c"));
-  } catch (e) {
-    exception = e;
-  };
-};
-
-Debug.setListener(listener);
-
-var c = "c";
-f();