epersonregistrations.md: clarify eperson registration / password reset POST endpoint description - #346

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: toshimaru/auto-author-assign@v2.0.1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/