next.js

c623a3fa - docs: remove reference to `createNextDescribe` in favor of `nextTestSetup` (#62245)

docs: remove reference to `createNextDescribe` in favor of `nextTestSetup` (#62245) Rendered: https://github.com/vercel/next.js/blob/hrmny/next-test-setup-docs/contributing/core/testing.md (the same except for `createNextDescribe` being replaced with `nextTestSetup`) Also split up the lines a bit and ran a grammar checker over it. Closes PACK-2536 --------- Co-authored-by: Balázs Orbán <info@balazsorban.com>