COMP: Bump actions/checkout from 6 to 7 in the actions group - #9

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: gsactions/commit-message-checker@16fa2d5de096ae0d35626443bcd24f1e756cafee. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/