Update supported system versions of Debian packages

[jiasli]

• Updated supported versions according to [Packaging] Bump embedded Python to 3.8 for deb packages Azure/azure-cli#20869, [Packaging] Add Ubuntu 21.10 Impish Indri support and drop Ubuntu 21.04 Hirsute Hippo support Azure/azure-cli#21151
• Refine the warning added by Add warning for dropping Ubuntu 14.04 (Trusty Tahir) and Debian 8 (Jessie) support #2968

[opbld33]

Docs Build status updates of commit 3ce0091:

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docs-ref-conceptual/includes/cli-install-linux-apt.md	✅Succeeded	View

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[jiasli]

PMC currently doesn't support debs built by Ubuntu 21.10 Impish, as explained in Azure/azure-cli#21151 (comment). Removing Impish.

[opbld31]

Docs Build status updates of commit 708003b:

✅ Validation status: passed

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docs-ref-conceptual/includes/cli-install-linux-apt.md	✅Succeeded	View

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[opbld33]

Docs Build status updates of commit a1b2f96:

✅ Validation status: passed

File	Status	Preview URL	Details
docs-ref-conceptual/includes/cli-install-linux-apt.md	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching the docs.microsoft.com contributor guides
• Post your question in the Docs support channel