[FIX] Update outdated Node.js and Deno requirements in Development Guidelines

[rishika-2626]

I noticed that the Development Guidelines in the Handbook still mention Node v14.17.0 and Fibers.

However, the current Rocket.Chat develop branch requires Node v22.16.0 and Deno for the Apps-Engine. This inconsistency is causing build failures for new contributors following the guide.

I have a PR ready to update these requirements to match the current 2026 build standards.