Mark use of deprecated type. (#106282)

diff --git a/packages/flutter/test/foundation/_compute_caller_unsound_null_safety_error.dart b/packages/flutter/test/foundation/_compute_caller_unsound_null_safety_error.dart
index 8ceaddb..9716700 100644
--- a/packages/flutter/test/foundation/_compute_caller_unsound_null_safety_error.dart
+++ b/packages/flutter/test/foundation/_compute_caller_unsound_null_safety_error.dart
@@ -16,7 +16,7 @@
   try {
     await compute(throwNull, null);
   } catch (e) {
-    if (e is! NullThrownError) {
+    if (e is! NullThrownError) { // ignore: deprecated_member_use
       throw Exception('compute returned bad result');
     }
   }