Update installation document

[k82cn]

Currently, Flame has flmadm to install Flame in bare metal host; it's better to update installation document based on that as we did not support Kubernetes right now.

[xflops-bot]

Thanks for raising this, @k82cn!

You make a great point. Since flmadm is the current supported method for installing Flame on bare metal hosts and Kubernetes support isn't available yet, it makes sense to update the installation documentation to reflect this.

Here's what I suggest for the documentation update:

1. Focus on flmadm - Make it the primary (or only) installation method documented
2. Remove/defer Kubernetes references - Either remove Kubernetes installation instructions or clearly mark them as "coming soon" / "not yet supported"
3. Add clear prerequisites - Document the bare metal host requirements for flmadm
4. Include usage examples - Provide step-by-step instructions for common flmadm commands

Would you like me to help draft the updated documentation, or is there an existing PR in progress for this? Also, are there any specific flmadm features or workflows that should be highlighted in the docs?