Add test coverage for `createAlert` usage in ee/app/assets/javascripts/security_dashboard/components/instance/project_manager.vue
While replacing createFlash by createAlert we have realised the gap of coverage for the createAlert usage. Sometimes we modified several components and modules but that didn't reflected in any change in the specs (see for example this MR)
createAlert is sometimes used to warn the user about unusual errors. One reason for the coverage gap could be that developers may have found difficulties recreating these errors states.
In this issue we advocate to improve the coverage for the use of createAlert.