Use build_stubbed to avoid interacting with the DB in todos helper specs

changelogs/unreleased/perf-use-build-stubbed.yml

+---
+title: Use build_stubbed to avoid interacting with the DB in todos helper specs
+merge_request: 32906
+author: Arun Kumar Mohan
+type: performance

spec/helpers/todos_helper_spec.rb

@@ -89,7 +89,7 @@ describe TodosHelper do
 
     context 'when given a non-design todo' do
       let(:todo) do
-        create(:todo, :assigned,
+        build_stubbed(:todo, :assigned,
         user: user,
         project: issue.project,
         target: issue,