Remove destructuring and default arguments runtime flags

test/mjsunit/es6/regress/regress-4395.js

 // Copyright 2015 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-destructuring-bind --harmony-default-parameters
 
 (function testExpressionTypes() {
   "use strict";
   ((x, y = x) => assertEquals(42, y))(42);
 
   ((x, y = (x)) => assertEquals(42, y))(42);
   ((x, y = `${x}`) => assertEquals("42", y))(42);
   ((x, y = x = x + 1) => assertEquals(43, y))(42);
   ((x, y = x()) => assertEquals(42, y))(() => 42);
   ((x, y = new x()) => assertEquals(42, y.z))(function() { this.z = 42 });
@@ skipping 79 matching lines @@
   }
 
   new D();
 })();
 
 
 (function testScopeFlags() {
   ((x, y = eval('x')) => assertEquals(42, y))(42);
   ((x, {y = eval('x')}) => assertEquals(42, y))(42, {});
 })();