Resolve "Fix `spec/frontend/content_editor/components/wrappers/code_block_spec.js`"

What does this MR do and why?

Close #483193

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Before	After

How to set up and validate locally

Run the spec in Vue 2 and Vue 3 mode:

yarn jest app/assets/javascripts/content_editor/components/wrappers/code_block.vue

VUE_VERSION=3 yarn jest app/assets/javascripts/content_editor/components/wrappers/code_block.vue