Add Oracle Linux installation instructions

[villepeh]

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
  • Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
• Code style is correct
  (run the linters)

I forgot the guide applies to Oracle Linux as well. In fact, I ran a small homeserver on OEL a few months back.

I did minimal installations on Rocky and OEL on VirtualBox and noticed Codeready/Powertools repos aren't required, so I removed those commands from the guide. I switched RHEL-references to EL.

#17423 was merged before I remembered about OEL but a new PR shouldn't hurt :)