Remove unnecessary loop in a test.

tests/language/optimized_setter_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Test various setter situations, testing special cases in optimizing compiler.
 // VMOptions=--optimization-counter-threshold=10 --no-use-osr
 
 import "package:expect/expect.dart";
 
 class A {
   int field = 0;
@@ skipping 126 matching lines @@
     Expect.equals(12, z.pField);
     Expect.equals(12, r);
   }
   A a = new A();
   var r = oneTarget(a, 11);
   Expect.equals(11, a.field);
   Expect.equals(11, r);
 }
 
 void main() {
-  for (int i = 0; i< 20; i++) {}
   sameImplicitSetter();
   setterNoFeedback();
   sameNotImplicitSetter();
 
   multiImplicitSetter();
   multiNotImplicitSetter();
 }