chore: drop `form-data` (#57141)
### What?
Dropping `form-data` polyfill as Node.js 18+ versions all expose it on `globalThis`
### Why?
Reduce the amount of shipped code in Next.js
### How?
Similar to #56899
See: https://nodejs.org/docs/latest-v18.x/api/globals.html#class-formdata
