Remove an unneeded ignore comment in vm package

Change-Id: I3b81e1d66c2100b8ed1834815f318cf39a8da305
Tested: This only impacts the analyzer's reporting of diagnostics, so I ran the analyzer over the code and verified that no new diagnostics were being reported.
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/238983
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
diff --git a/pkg/vm/testcases/transformations/ffi/finalizable_sync3.dart b/pkg/vm/testcases/transformations/ffi/finalizable_sync3.dart
index bc83bbe..75ca4d7 100644
--- a/pkg/vm/testcases/transformations/ffi/finalizable_sync3.dart
+++ b/pkg/vm/testcases/transformations/ffi/finalizable_sync3.dart
@@ -4,8 +4,6 @@
 
 // @dart=2.16
 
-// ignore_for_file: unused_local_variable
-
 import 'dart:ffi';
 
 class MyFinalizable implements Finalizable {