Remove unnecessary tests

pkg/analysis_server/test/search/element_references_test.dart

Index: pkg/analysis_server/test/search/element_references_test.dart
diff --git a/pkg/analysis_server/test/search/element_references_test.dart b/pkg/analysis_server/test/search/element_references_test.dart
index 25a7b3fb9414178b95206e623e9a2b036cfb2117..35a78ee431076f006051ab53214c37d63bdf768d 100644
--- a/pkg/analysis_server/test/search/element_references_test.dart
+++ b/pkg/analysis_server/test/search/element_references_test.dart
@@ -6,7 +6,6 @@ import 'dart:async';
 
 import 'package:analysis_server/protocol/protocol.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
-import 'package:analysis_server/src/services/index/index.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -15,7 +14,6 @@ import 'abstract_search_domain.dart';
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ElementReferencesTest);
-    defineReflectiveTests(_NoSearchEngine);
   });
 }
 
@@ -672,25 +670,3 @@ class A<T> {
     assertHasResult(SearchResultKind.REFERENCE, 'T m()');
   }
 }
-
-@reflectiveTest
-class _NoSearchEngine extends AbstractSearchDomainTest {
-  @override
-  Index createIndex() {
-    return null;
-  }
-
-  test_requestError_noSearchEngine() async {
-    addTestFile('''
-main() {
-  var vvv = 1;
-  print(vvv);
-}
-''');
-    Request request = new SearchFindElementReferencesParams(testFile, 0, false)
-        .toRequest('0');
-    Response response = await waitResponse(request);
-    expect(response.error, isNotNull);
-    expect(response.error.code, RequestErrorCode.NO_INDEX_GENERATED);
-  }
-}