Resolve "Tooltips on note timestamps not showing for issues"

What does this MR do?

EE counterpart for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30846

In this MR I've upgraded @gitlab/ui to the latest version (that includes latest bootstrap-vue). Tooltip bug was cause by Bootstrap Vue directive trying to access Vue Router in the root instance; this behavior was fixed in the Bootstrap Vue library itself as described here: https://gitlab.com/gitlab-org/gitlab-ce/issues/64669#note_192647743

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content