test: don't use __dirname in tailwind config

[sapphi-red]

Description

require(esm) is now enabled by default from Node 22.12.0.
Before node 22.12.0, the tailwind config was loaded by jiti and that allowed users to use __dirname in ESM tailwind configs.
But after node 22.12.0, require(esm) is supported by Node and that is used instead of jiti and thus __dirname is not declared and errors.

https://github.com/tailwindlabs/tailwindcss/blob/f875ab9706cae8262e15e5b382580fc8e2d4197f/src/lib/load-config.ts#L34-L51

[hi-ogawa]

How does node 18, 20 work (before and after this PR)? Is it still go to lazyJiti fallback in L50?

[sapphi-red]

On node 18 / 20, before this PR, require throws ERR_REQUIRE_ESM error, so lazyJiti will be called and uses sucrase for the transform. After this PR, require still throws ERR_REQUIRE_ESM error and lazyJiti will be called, but babel will be used for the transform.

[hi-ogawa]

Testing locally, I'm not sure what's happening with require(esm) error and try/catch. It looks try/catch is called but still unhandle errors somewhere?