Resolve "Migrate spec/javascripts/ide/components/preview/clientside_spec.js to Jest"

What does this MR do?

Migrates clientside_spec.js to Jest & vue-test-utils

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• [-] 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

Issue: #66676 (closed)