Add documentation for displaying the TOTP secret key during enrollment in IS 7.1 - #6301

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/

[vale] reported by reviewdog 🐶 Did you really mean 'onwards'? Raw Output: {"message":"Did you really mean 'onwards'?","location":{"path":"en/includes/guides/authentication/mfa/add-totp-login.md","range":{"start":{"line":124,"column":69},"end":{"line":124,"column":76}}},"severity":"WARNING","code":{"value":"Vale.Spelling"}}