enable lint prefer_final_in_for_each (#47724)

packages/flutter_tools/lib/src/vmservice.dart

diff --git a/packages/flutter_tools/lib/src/vmservice.dart b/packages/flutter_tools/lib/src/vmservice.dart
index 9d0450e..99adc78 100644
--- a/packages/flutter_tools/lib/src/vmservice.dart
+++ b/packages/flutter_tools/lib/src/vmservice.dart
@@ -856,7 +856,7 @@
   void _removeDeadIsolates(List<Isolate> newIsolates) {
     // Build a set of new isolates.
     final Set<String> newIsolateSet = <String>{};
-    for (Isolate iso in newIsolates) {
+    for (final Isolate iso in newIsolates) {
       newIsolateSet.add(iso.id);
     }