Remove --harmony-async-await runtime flag

test/debugger/debug/es8/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";
 
@@ skipping 13 matching lines @@
     assertEquals("c", exec_state.frame(2).evaluate("c"));
   } catch (e) {
     exception = e;
   };
 };
 
 Debug.setListener(listener);
 
 var c = "c";
 f();