Remove --harmony-arrow-functions flag

test/mjsunit/harmony/regress/regress-4160.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-arrow-functions --allow-natives-syntax
-
-(function(x) {
-  (function(x) {
-    var boom = (() => eval(x));
-    assertEquals(23, boom());
-    assertEquals(23, boom());
-    %OptimizeFunctionOnNextCall(boom);
-    assertEquals(23, boom());
-    assertEquals("23", x);
-  })("23");
-  assertEquals("42", x);
-})("42");
-
-(function(x) {
-  (function(x) {
-    var boom = (() => (eval("var x = 66"), x));
-    assertEquals(66, boom());
-    assertEquals(66, boom());
-    %OptimizeFunctionOnNextCall(boom);
-    assertEquals(66, boom());
-    assertEquals("23", x);
-  })("23");
-  assertEquals("42", x);
-})("42");