Clarify install target docs. - #929

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/setup-node@v4, conda-incubator/setup-miniconda@3b0f2504dd76ef23b6d31f291f4913fb60ab5ff3. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Mamba support is still experimental and can result in differently solved environments!