Add missing spec for gitlab schema

.rubocop.yml

@@ -393,7 +393,6 @@ RSpec/RepeatedExample:
     - 'spec/features/projects/files/template_type_dropdown_spec.rb'
     - 'spec/finders/environments_finder_spec.rb'
     - 'spec/frontend/fixtures/merge_requests.rb'
-    - 'spec/graphql/gitlab_schema_spec.rb'
     - 'spec/helpers/users_helper_spec.rb'
     - 'spec/lib/gitlab/closing_issue_extractor_spec.rb'
     - 'spec/lib/gitlab/import_export/project/relation_factory_spec.rb'

changelogs/unreleased/gitlab-schema-spec.yml

+---
+title: Add missing spec for gitlab schema
+merge_request: 28855
+author: Rajendra Kadam
+type: added

spec/graphql/gitlab_schema_spec.rb

@@ -10,8 +10,8 @@ describe GitlabSchema do
     expect(field_instrumenters).to include(BatchLoader::GraphQL)
   end
 
-  it 'enables the preload instrumenter' do
-    expect(field_instrumenters).to include(BatchLoader::GraphQL)
+  it 'enables the generic instrumenter' do
+    expect(field_instrumenters).to include(instance_of(::Gitlab::Graphql::GenericTracing))
   end
 
   it 'enables the authorization instrumenter' do