chore: bump `actions/checkout` to `v3` (#36937)

Summary:
A recent [Rebase run](https://github.com/facebook/react-native/actions/runs/4724279197/jobs/8381306851) gave following warning:
>Node.js 12 actions are *deprecated*. Please update the following actions to use Node.js 16: actions/checkout@v2. For more information see: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/.

So, it makes sense to upgrade to `actions/checkout@v3`.

## Changelog:

[GENERAL] [SECURITY] - Bump `actions/checkout` to `v3`

Pull Request resolved: https://github.com/facebook/react-native/pull/36937

Test Plan: - ci should be green + the `/rebase` command works as usual.

Reviewed By: rshest

Differential Revision: D45079793

Pulled By: cortinico

fbshipit-source-id: 49e654cf15f6ae7208bf8b277a194ace3fa62aa0