Remove FLAG_min_preparse_length.

test/mjsunit/es6/classes-lazy-parsing.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: --min-preparse-length=0
-
 'use strict';
 
 class Base {
   m() {
     return 42;
   }
 }
 
 class Derived extends Base {
   m() {
     return super.m();
   }
   evalM() {
     return eval('super.m()');
   }
 }
 
 assertEquals(42, new Derived().m());
 assertEquals(42, new Derived().evalM());
 
 
 class LazyDerived extends Base {
   constructor() {
     eval('super()');
   }
 }
 assertInstanceof(new LazyDerived(), LazyDerived);
 assertInstanceof(new LazyDerived(), Base);