Remove support for legacy const, part 1

test/mjsunit/regress/regress-3138.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: --legacy-const
-
 (function f(){
    assertEquals("function", typeof f);
 })();
 
 (function f(){
    var f;  // Variable shadows function name.
    assertEquals("undefined", typeof f);
 })();
 
 (function f(){
    var f;
    assertEquals("undefined", typeof f);
    with ({});  // Force context allocation of both variable and function name.
 })();
 
 assertEquals("undefined", typeof f);
 
 // var initialization is intercepted by with scope.
 (function() {
   var o = { a: 1 };
   with (o) {
     var a = 2;
   }
   assertEquals("undefined", typeof a);
   assertEquals(2, o.a);
 })();
-
-// const initialization is not intercepted by with scope.
-(function() {
-  var o = { a: 1 };
-  with (o) {
-    const a = 2;
-  }
-  assertEquals(2, a);
-  assertEquals(1, o.a);
-})();