Add missing hyphen in className of layout.tsx

[Hahlh]

I discovered this one while completely changing the styling, so please mind that this fix might lead to breakage.

Testing with the knowledge of what the intended styling is supposed to look like is required.

[vercel[bot]]

@Hahlh is attempting to deploy a commit to the Vercel Solutions Team on Vercel.

A member of the Team first needs to authorize it.