[bootstrapper] Ensure RegExp constructor has fast properties.

test/mjsunit/regress/regress-5902.js

 // Copyright 2017 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: --allow-natives-syntax
 
 var log = [];
 
 function check(predicate, item) {
   if (!predicate) log.push(item);
@@ skipping 37 matching lines @@
   if (!%IsJSReceiver(prototype_constructor)) return;
   check(
       %HasFastProperties(prototype_constructor),
       `${name}.prototype.constructor`);
 });
 
 // This is the current set of dictionary mode objects.
 // Remove items as we fix them. See issue 5902.
 assertEquals(
     [
-      'RegExp', 'RegExp.prototype.constructor', 'Error.prototype',
+      'Error.prototype',
       'EvalError.prototype', 'RangeError.prototype', 'ReferenceError.prototype',
       'SyntaxError.prototype', 'TypeError.prototype', 'URIError.prototype',
       'Map', 'Map.prototype.constructor', 'Set', 'Set.prototype.constructor'
     ],
     log);