Removing unnecessary test file (#485)

material_theme_builder/test/widget_test.dart

@@ -1,11 +0,0 @@
-// Copyright 2019 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:flutter_test/flutter_test.dart';
-
-void main() {
-  testWidgets('Empty test', (tester) async {
-    expect(1, 1);
-  });
-}