Remove obsolete --harmony-promises flag from tests.

test/mjsunit/es6/debug-promises-throw-in-reject.js

 // Copyright 2014 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-promises --expose-debug-as debug
+// Flags: --expose-debug-as debug
 
 // Test debug events when an exception is thrown inside a Promise, which is
 // caught by a custom promise, which throws a new exception in its reject
 // handler.  We expect an Exception debug event with a promise to be triggered.
 
 Debug = debug.Debug;
 
 var log = [];
 var step = 0;
 
@@ skipping 36 matching lines @@
     // and this listener to be executed after the main script is finished.
     print("Unexpected exception: " + e + "\n" + e.stack);
     quit(1);
   }
 }
 
 Debug.setBreakOnUncaughtException();
 Debug.setListener(listener);
 
 log.push("end main");