fix: Delete yarn.lock to make Prisma not assume you are using Yarn

[janpio]

... which might not actually be installed on the developer's machine.

Triggered by discussion in https://prisma-company.slack.com/archives/C02UA0D53KM/p1651666404131349

Npm lockfile might also need to go based on result of https://github.com/vercel/next.js/discussions/36677