docs: fix isNan to isNaN

[Omochice]

Summary

The https://biomejs.dev/linter/rules/use-number-namespace/ page says isNan, but actually isNaN, so I fixed it.

Test Plan

No(only docs).

[codspeed-hq]

CodSpeed Performance Report

Merging #4106 will improve performances by 7.04%

_{Comparing Omochice:main (624bbfe) with main (75b4387)}

Summary

⚡ 1 improvements
✅ 106 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	Omochice:main	Change
⚡	db_17847247775464589309.json[cached]	14 ms	13.1 ms	+7.04%