Migrate ee/spec/javascripts/vue_mr_widget/ to Jest

Description

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

See the related epic for how to do this.

• ee/spec/javascripts/vue_mr_widget/mock_data.js
• ee/spec/javascripts/vue_mr_widget/stores/mr_widget_store_spec.js
• ee/spec/javascripts/vue_mr_widget/components/mr_widget_pipeline_container_spec.js
• ee/spec/javascripts/vue_mr_widget/components/performance_issue_body_spec.js
• ee/spec/javascripts/vue_mr_widget/components/states/mr_widget_auto_merge_enabled_spec.js
• ee/spec/javascripts/vue_mr_widget/components/approvals/approvals_auth_spec.js
• ee/spec/javascripts/vue_mr_widget/components/approvals/approvals_spec.js
• ee/spec/javascripts/vue_mr_widget/components/codequality_issue_body_spec.js
• ee/spec/javascripts/vue_mr_widget/mr_widget_pipeline_spec.js
• ee/spec/javascripts/vue_mr_widget/ee_mr_widget_options_spec.js