Update GitHub Actions to use Node 20

[albertvillanova]

Currently, we get deprecation warnings when building our docs: https://github.com/huggingface/datasets/actions/runs/9547896244

build / build_main_documentation
Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v2, actions/setup-node@v3. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

This PR updates the required GitHub Actions to use Node 20.

[albertvillanova]

There was still one deprecation warning: https://github.com/huggingface/doc-builder/actions/runs/9561218485

integration_doc_build
Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/cache@v2. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

[albertvillanova]

We are still getting the deprecation warnings: https://github.com/huggingface/datasets/actions/runs/10402495585

build / build_main_documentation
The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

build / build_main_documentation
The following actions use a deprecated Node.js version and will be forced to run on node20: actions/checkout@v2, actions/setup-node@v3. For more info: https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/

[albertvillanova]

Thanks for the merge, @coyotte508. 🤗