test: rename node_modules_bak to node_modules (#62066)
We switched to `pnpm` for testing instead of `yarn` for e2e tests
containing customized node_modules packages, it works with
`node_modules` folder before. Rename the existing `node_modules_bak`
hack to make it easy to test with.
Previously we use `yarn` but it will clean `node_modules` folder so we
have to use another script to copy packages, it's not a required thing
now so we can test package from node_modules directly without renaming
folders locally
Closes NEXT-2496
