Remove method refactored out to a spec helper

Made available in gitlab.com/gitlab-org/gitlab/-/merge_requests/39164

spec/controllers/projects/ci/daily_build_group_report_results_controller_spec.rb

@@ -149,8 +149,4 @@ RSpec.describe Projects::Ci::DailyBuildGroupReportResultsController do
       date: date
     )
   end
-
-  def csv_response
-    CSV.parse(response.body)
-  end
 end