fix: follow-ups to #1500 (README), #1515 (sql_limit) and #1566 (backslashes in Format SQL) - #1656

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/