Docs: Fixed syntax error in example of using yarn cache in gitlab CI

What does this MR do and why?

Fixes syntax in example of using yarn cache in gitlab CI because it was invalid.

Screenshots or screen recordings

How to set up and validate locally

Juset try it in Lint https://gitlab.nangu.tv/javascript/services/-/ci/lint

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.