[ES] Translate Chapter 12 Sections 4 to 7 (GRPO in TRL & Unsloth) - #1356

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/setup-python@e9aba2c848f5ebd159c070c61ea2c4e2b122355e. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/