Make it clear on install docs that Kali and Arch are unsupported community packages

[joeyaiello]

PR Summary

Per our conversation in shiproom, Kali and Arch are unsupported (not just experimental) and community-owned, and we should be clear as such.

PR Context

Select the type(s) of documents being changed.

Cmdlet reference & about_ topics

• Version 7 content
• Version 6 content
• Version 5.1 content

Conceptual articles

• Fundamental conceptual articles
• Script sample articles
• DSC articles
• Gallery articles
• JEA articles
• WMF articles
• SDK articles

PR Checklist

• I have read the contributors guide and followed the style and process guidelines
• PR has a meaningful title
• PR is targeted at the staging branch
• All relevant versions updated
• Includes content related to issues and PRs - see Closing issues using keywords.
• This PR is ready to merge and is not Work in Progress
  • If the PR is work in progress, please add the prefix WIP: or [ WIP ] to the beginning of the
    title and remove the prefix when the PR is ready.

[opbld33]

Docs Build status updates of commit f934e82:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/install/Installing-PowerShell-Core-on-Linux.md	✅Succeeded	View (powershell-3.0) View (powershell-4.0) View (powershell-5.0) View (powershell-5.1) View (powershell-6) View (powershell-7)

For more details, please refer to the build report.

Note: If you changed an existing file name or deleted a file, broken links in other files to the deleted or renamed file are listed only in the full build report.