fix: Crates.io package installation on Debian & Fedora

[koibtw]

Type of Change

• [x] Bug fix
• [x] Hotfix

Description

The script tries to install rustup, but Debian doesn't provide it in stable repos. That's why the installation failed on Chris' latest stream.

Checklist

• [x] My code adheres to the coding and style guidelines of the project.
• [x] I have performed a self-review of my own code.
• [x] My changes generate no errors/warnings/merge conflicts.