fix tiniest typo in readme

[zzstoatzz]

so small I considered not opening it but I'd want someone to do the same for me 😄

Checklist

• The pull request title is a good summary of the changes - it will be used in the changelog
• Unit tests for the changes exist
• Documentation reflects the changes where applicable
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[codspeed-hq]

CodSpeed Performance Report

Merging #9219 will not alter performance

_{Comparing zzstoatzz:patch-1 (c6ac91d) with main (7af856a)}

Summary

✅ 13 untouched benchmarks

[sydney-runkle]

Thanks!