Migrate packages/flutter_tools/test/web.shard (#110713)

packages/flutter_tools/test/web.shard/sdk_web_configuration_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:dwds/dwds.dart';
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
@@ -13,10 +11,10 @@ import 'package:flutter_tools/src/isolated/sdk_web_configuration.dart';
 import '../src/common.dart';
 
 void main() {
-  FileSystem fileSystem;
+  late FileSystem fileSystem;
 
   group('Flutter SDK configuration for web', () {
-    SdkConfiguration configuration;
+    late SdkConfiguration configuration;
 
     setUp(() async {
       fileSystem = MemoryFileSystem.test();