Fix warnings_checker.dart handling of multitests

tests/language/const_factory_with_body_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.
 //
 // Tests that a "const factory" with body produces a compile-time error.
 
 class ConstFactoryWithBody {
-  const factory ConstFactoryWithBody.one() { } // /// 01: compile-time error
+  const factory ConstFactoryWithBody.one() { } // //# 01: compile-time error
 }
 
 main() {
-  const ConstFactoryWithBody.one(); // /// 01: continued
+  const ConstFactoryWithBody.one(); // //# 01: continued
 }