Report HintCode.UNUSED_LOCAL_VARIABLE for local variables whose value is never used.

pkg/analysis_server/test/services/correction/fix_test.dart

Index: pkg/analysis_server/test/services/correction/fix_test.dart
diff --git a/pkg/analysis_server/test/services/correction/fix_test.dart b/pkg/analysis_server/test/services/correction/fix_test.dart
index 6060c940ba076ecfe00ba127fe844dcf8e3db87b..fb582b7da4063961a7fe05512bbbe807ccbabc4e 100644
--- a/pkg/analysis_server/test/services/correction/fix_test.dart
+++ b/pkg/analysis_server/test/services/correction/fix_test.dart
@@ -2304,6 +2304,9 @@ main() {
 
   AnalysisError _findErrorToFix() {
     List<AnalysisError> errors = context.computeErrors(testSource);
+    errors.removeWhere((error) {
+      return error.errorCode == HintCode.UNUSED_LOCAL_VARIABLE;
+    });
     if (checkHasSingleError) {
       expect(errors, hasLength(1));
     }