Remove incorrect localVue usage in ee/spec/frontend/vue_mr_widget

What does this MR do?

As described in &2360 (closed), cleans up our Jest tests from unnecessary localVue usage

Involved specs

• ee/spec/frontend/vue_mr_widget/components/approvals/approvals_footer_spec.js
• ee/spec/frontend/vue_mr_widget/components/approvals/approvals_list_spec.js
• ee/spec/frontend/vue_mr_widget/components/approvals/approvals_summary_optional_spec.js
• ee/spec/frontend/vue_mr_widget/components/approvals/approvals_summary_spec.js
• ee/spec/frontend/vue_mr_widget/components/approvals/approved_icon_spec.js
• ee/spec/frontend/vue_mr_widget/components/blocking_merge_requests/blocking_merge_requests_report_spec.js
• ee/spec/frontend/vue_mr_widget/components/merge_train_helper_text_spec.js
• ee/spec/frontend/vue_mr_widget/components/merge_train_position_indicator_spec.js
• ee/spec/frontend/vue_mr_widget/components/states/mr_widget_ready_to_merge_spec.js
• ee/spec/frontend/vue_mr_widget/components/visual_review_app_spec.js

Conformity

• Merge request performance guidelines
• Style guides

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Closes: #121739 (closed)