Revert of Add a separate scope for switch

test/mjsunit/regress/regress-4377.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.
-
-// See: http://code.google.com/p/v8/issues/detail?id=4377
-
-// Switch statements should introduce their own lexical scope
-
-'use strict';
-
-switch (1) { case 1: let x = 2; }
-
-assertThrows(() => x, ReferenceError);
-
-{
-  let result;
-  let x = 1;
-  switch (x) {
-    case 1:
-      let x = 2;
-      result = x;
-      break;
-    default:
-      result = 0;
-      break;
-  }
-  assertEquals(1, x);
-  assertEquals(2, result);
-}
-
-{
-  let result;
-  let x = 1;
-  switch (eval('x')) {
-    case 1:
-      let x = 2;
-      result = x;
-      break;
-    default:
-      result = 0;
-      break;
-  }
-  assertEquals(1, x);
-  assertEquals(2, result);
-}