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

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_shared/components/accordion/accordion_item_spec.js
• ee/spec/frontend/vue_shared/components/accordion/accordion_spec.js
• ee/spec/frontend/vue_shared/components/sidebar/epics_select/base_spec.js
• ee/spec/frontend/vue_shared/components/sidebar/epics_select/dropdown_search_input_spec.js
• ee/spec/frontend/vue_shared/security_reports/card_security_reports_app_spec.js
• ee/spec/frontend/vue_shared/security_reports/components/vulnerability_details_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: #121740 (closed)