Incus installation guide update for installing in Fedora 41+

[CC-Hsu]

Required information

• Distribution: Fedora
• Distribution version: 41
• The output of "incus info" or if that fails:
  • Kernel version: 6.11.10-300
  • LXC version: 6.0.2
  • Incus version: 6.2

Issue description

In the recent Fedora 41, Incus-6.2 is included in the official repository.

https://packages.fedoraproject.org/pkgs/incus/

But currently the documentation is not update yet.
https://linuxcontainers.org/incus/docs/main/installing/
https://github.com/lxc/incus/blob/main/doc/installing.md

I think the below paragraph can be included. (borrowed from Ubuntu installation tab)

A native incus package is currently available in Fedora 41 and later. On such systems, just running `dnf install incus` will get Incus installed.

Best Regards.