Remove unused reference to SearchEngine

pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart

Index: pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart
diff --git a/pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart b/pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart
index 34271aa6e0e63cd59142ac90db5684dfef88107e..04f7b783344dafd529fbca15302270e4b19a2cd4 100644
--- a/pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart
+++ b/pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart
@@ -8,7 +8,6 @@ import 'package:analysis_server/src/ide_options.dart';
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/services/completion/dart/imported_reference_contributor.dart';
-import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:test/test.dart';
@@ -3557,12 +3556,6 @@ class C extends B with M1, M2 {
     // Resolve the source in the 2nd context and update the index
     var result = context2.performAnalysisTask();
     while (result.hasMoreWork) {
-      result.changeNotices.forEach((ChangeNotice notice) {
-        CompilationUnit unit = notice.resolvedDartUnit;
-        if (unit != null) {
-          index.indexUnit(unit);
-        }
-      });
       result = context2.performAnalysisTask();
     }