Format all tests.

tests/language/issue21957_test.dart

 // Copyright (c) 2014, 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.
 
 // Check slow path for PotentialUnboxedStore.
 // VMOptions=--optimization_counter_threshold=-1
 
 main() {
   for (int i = 0; i < 1000000; i++) {
     new A();
   }
 }
 
 class A {
   var a = 1.0;
 }
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