I forked and ran your repo and got the failure you described. Updating the dependencies as described in numerous recent threads on the python data analysis projects (specifically, I set python = "^3.10" in pyproject.toml, uninstalled all packages in the package tool and reinstalled seaborn, which pulled in seaborn 0.12.1, matplotlib 3.6.2, numpy 1.23.5, and pandas 1.5.2) and re-running the tests resulted in all passing.
I was able to replicate this on a local machine, so this is definitely an “update the dependencies” issue.