Correct file names for tests in tests/language.

tests/language/optimized_hoisting_checked_mode_assert.dart

-// Copyright (c) 2012, 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 checked mode assertions inside loops.
-
-int foo(x, n)  {
-  double z = 0.0;
-  for (var i=0; i<n; i++) {
-    double z = x;
-  }
-  return 0;
-}
-
-main() {
-  for (var i=0; i<10000; i++) foo(1.0, 10);
-  Expect.equals(0, foo(1.0, 10));
-  Expect.equals(0, foo(2, 0));  // Must not throw in checked mode.
-}
-