Migrate spec/javascripts/pages/ to Jest

Description

Let's migrate the specs in spec/javascripts/pages/ from Karma to Jest.

See the related epic for how to do this.

• spec/javascripts/pages/projects/pipeline_schedules/shared/components/interval_pattern_input_spec.js !31501 (merged)
• spec/javascripts/pages/projects/pipeline_schedules/shared/components/pipeline_schedule_callout_spec.js !32506 (merged)
• spec/javascripts/pages/admin/application_settings/account_and_limits_spec.js !32506 (merged)
• spec/javascripts/pages/admin/users/new/index_spec.js !32506 (merged)
• spec/javascripts/pages/admin/jobs/index/components/stop_jobs_modal_spec.js !32506 (merged)
• spec/javascripts/pages/labels/components/promote_label_modal_spec.js !32506 (merged)
• spec/javascripts/pages/sessions/new/preserve_url_fragment_spec.js !32506 (merged)
• spec/javascripts/pages/milestones/shared/components/delete_milestone_modal_spec.js !32506 (merged)
• spec/javascripts/pages/milestones/shared/components/promote_milestone_modal_spec.js !32506 (merged)