## Summary

Coming from the conversation from here:
https://github.com/elastic/kibana/pull/225339#discussion_r2167248942

 and
a proposal from @akowalska622, we noticed that the useMemoCss doesn't
catch the keys of the css object. This fixes it.

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Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>