Refactor ci_icon_spec to use vue-test-utils

What does this MR do?

This refactors the ci_icon_spec.js file to use vue-test-utils instead of the previous mountComponent helper function

#300672 (closed)

Screenshots (strongly suggested)

N/A

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content