chore: simplify prettier config

[aslilac]

Pretty much all of the settings in the prettier config here are either in conflict with coder/coder, or are just the defaults now. We can just remove the whole file to get closer to matching coder/coder.

[aslilac]

I would also like to switch this repository to tabs, but that will be a much bigger diff.

I decided I might as well make the diff bigger. Go big or go home.

[matifali]

We don't use prettier in coder/coder anymore. Maybe move to biome here too.

[aslilac]

I think the editor integration for prettier is pretty universally better. in a smaller repo like this where it's fast enough I actually think it's better to stick with prettier.