Remove useless dart2js_extra/class_test

TBR=johnniwinther@google.com

Change-Id: I2c6b08f139e3404961a91166d6f2393e935ccd0f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108368
Reviewed-by: Stephen Adams <sra@google.com>
Commit-Queue: Stephen Adams <sra@google.com>

tests/compiler/dart2js_extra/class_test.dart

@@ -1,15 +0,0 @@
-// 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.
-
-class Foo {
-  fisk() {
-    print('in fisk');
-  }
-}
-
-void main() {
-  // TODO(ahe): Should be "new Foo()" instead of "null".
-  Foo x = null;
-  x.fisk();
-}