Remove dead code for an unused (old) task

pkg/analyzer/test/generated/engine_test.dart

Index: pkg/analyzer/test/generated/engine_test.dart
diff --git a/pkg/analyzer/test/generated/engine_test.dart b/pkg/analyzer/test/generated/engine_test.dart
index f5a4c016165bef81143eba87f2dc8845268bd30c..eb87ea7897f9da7254f200b760a922b99de0e40c 100644
--- a/pkg/analyzer/test/generated/engine_test.dart
+++ b/pkg/analyzer/test/generated/engine_test.dart
@@ -33,7 +33,6 @@ import 'package:analyzer/src/generated/testing/element_factory.dart';
 import 'package:analyzer/src/generated/utilities_collection.dart';
 import 'package:analyzer/src/services/lint.dart';
 import 'package:analyzer/src/string_source.dart';
-import 'package:analyzer/src/task/task_dart.dart';
 import 'package:analyzer/task/model.dart' hide AnalysisTask;
 import 'package:html/dom.dart' show Document;
 import 'package:path/path.dart' as pathos;
@@ -6382,12 +6381,6 @@ class TestAnalysisContext_test_setSourceFactory extends TestAnalysisContext {
  */
 class TestTaskVisitor<E> implements AnalysisTaskVisitor<E> {
   @override
-  E visitBuildUnitElementTask(BuildUnitElementTask task) {
-    fail("Unexpectedly invoked visitGenerateDartErrorsTask");
-    return null;
-  }
-
-  @override
   E visitGenerateDartErrorsTask(GenerateDartErrorsTask task) {
     fail("Unexpectedly invoked visitGenerateDartErrorsTask");
     return null;