docs: Refactor the installation instructions for s-nomp

[upbqdn]

Motivation

When working on #7423, I noticed our documentation for mining with s-nomp was outdated.

Solution

• Don't mention the getblocktemplate-rpcs feature anymore.
• Refactor the installation instructions for s-nomp. I only did this refactor for the Arch Linux section.

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

[upbqdn]

Note that I refactored the install instructions only for the Arch Linux section.

[upbqdn]

Note that I refactored the install instructions only for the Arch Linux section.

Also, the general instructions don't work anymore as they miss some necessary steps, such as using Python 3.10. I updated only the Arch section since I tested the new instructions only on that distribution. I thought this is acceptable since we don't plan to rely on s-nomp substantially.

[teor2345]

I think that's fine for now