Draft: Resolve "Replace vue_shared tooltip with GitLab UI’s tooltip in app/assets/javascripts/vue_merge_request_widget/components/mr_widget_header.vue"

What does this MR do?

Screenshots

Before	After

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Code review guidelines
• 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.
• Tested in all supported browsers

Related to #228984 (closed)