It fixes the fallback font used by browser in case of unsupported characters by the current subset of the Poppins web font (i.e. latin-ext characters).
This is the quickest solution to fix the problem. Additionally, you might want to update the Poppins font to contain a larger subset of characters.
PR introducing the self-hosted Poppins: Custom host fonts by iHiD · Pull Request #5905 · exercism/website · GitHub
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