Clean up and refactor FE Spec

Once the REST code is removed or at least fully migrated to GraphQL, let's clean up this existing spec file:

ee/spec/frontend/vue_merge_request_widget/widgets/security_reports/mr_widget_security_reports_spec.js

  1. Remove any duplicated code
  2. Remove any unused code
  3. Refactor if needed
Edited by 🤖 GitLab Bot 🤖