[docs] adjusted the code example for quickFilterValues

[michelengelen]

• [ ] I have followed (at least) the PR section of the contributing guide.

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adjusted the value in the code example to represent what is shown in the example Fixes #12912

[mui-bot]

Deploy preview: https://deploy-preview-12919--material-ui-x.netlify.app/

Updated pages:

• docs/data/data-grid/filtering/quick-filter.md

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