enable lint prefer_final_in_for_each (#47724)

diff --git a/packages/flutter_tools/test/general.shard/plugins_test.dart b/packages/flutter_tools/test/general.shard/plugins_test.dart
index 7d2d821..30b4401 100644
--- a/packages/flutter_tools/test/general.shard/plugins_test.dart
+++ b/packages/flutter_tools/test/general.shard/plugins_test.dart
@@ -208,7 +208,7 @@
     pluginClass: UseNewEmbedding
 dependencies:
 ''');
-      for (String dependency in dependencies) {
+      for (final String dependency in dependencies) {
         pluginDirectory
           .childFile('pubspec.yaml')
           .writeAsStringSync('  $dependency:\n', mode: FileMode.append);