Remove outdated yarn.lock in CodeSandbox repros

[karlhorky]

Closes #57896
Closes #63038

What?

Remove the outdated yarn.lock file that CodeSandbox saves between sandbox starts

Why?

As confirmed with @CompuIves, CodeSandbox caches the yarn.lock file generated after the first start + yarn install of a GitHub template (Yarn v1) - this saves old versions of Next.js (not the latest canary) in the lockfile and causes old versions of Next.js to be installed when users click on the CodeSandbox Reproduction link during issue creation.

This leads to the current breakage, where Next.js actually cannot even start in the reproduction sandbox:

1. Start creating a new GitHub issue on the vercel/next GitHub repo
2. Open the CodeSandbox reproduction link linked in the Link to the code that reproduces this issue section
3. Observe the error message below in the dev task started below (experimental.appDir: true was required in the 13.0.8-canary.0 version of Next.js in the cached yarn.lock file, but the next.config.js file no longer includes this config)

$ yarn dev
yarn run v1.22.19
$ next dev
ready - started server on 0.0.0.0:3000, url: http://localhost:3000
Error: > The `app` directory is experimental. To enable, add `appDir: true` to your `next.config.js` configuration under `experimental`. See https://nextjs.org/docs/messages/experimental-app-dir-config
    at Object.findPagesDir (/project/sandbox/node_modules/next/dist/lib/find-pages-dir.js:80:19)
    at new DevServer (/project/sandbox/node_modules/next/dist/server/dev/next-dev-server.js:110:59)
    at NextServer.createServer (/project/sandbox/node_modules/next/dist/server/next.js:140:20)
    at /project/sandbox/node_modules/next/dist/server/next.js:155:42
    at async NextServer.prepare (/project/sandbox/node_modules/next/dist/server/next.js:130:24)
    at async /project/sandbox/node_modules/next/dist/cli/next-dev.js:344:17
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Sandbox demo: https://codesandbox.io/p/sandbox/quirky-pascal-n32xk2?file=%2Fnext.config.js%3A5%2C1

How?

Remove (using rm) the outdated yarn.lock file

Caveats

This uses CodeSandbox-specific config, which is potentially unwanted, eg. this comment by @balazsorban44

• Upgrade Node.js to fix repro templates (16 -> LTS) #57871 (review)

Alternatives considered

• Commit an empty yarn.lock file to block caching of this file, PR open here: Add empty yarn.lock to prevent caching #57896
• Switch Yarn v1 to pnpm in repros: Switch CodeSandbox repros to pnpm #63038

cc @balazsorban44 @CompuIves

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 5e5cff0

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 9eeac6d

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer