message: refactor(core): remove unused export
  This export used to be here to turn this file into an ES Module - this is no longer needed
  because the file contains imports.
  PR Close
diff: @@ -26,7 +26,3 @@ if (_global.beforeEach) {
  resetFakeAsyncZone();
  });
  }
  -
  -// TODO(juliemr): remove this, only used because we need to export something to have compilation
  -// work.
  -export const __core_private_testing_placeholder__ = '';
  