docs: Update installation.md

[tomthetommy]

Description

This isn't very user friendly, and breaks the "copy" functionality. So I am proposing we remove the dollar signs and tee the yum repo into the file, preserving sudo.

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[CLAassistant]

All committers have signed the CLA.

[knqyf263]

Thanks!