Bump @babel/core, @babel/cli, @babel/plugin-transform-runtime, @babel/preset-env, @babel/register and fetch-mock - #446

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, actions/setup-node@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/