Update Ubuntu 20.04 base OS support wording in system overview

[ThatStoney]

What is being changed

This updates the "Operating system, software, and patches" section of the GitHub Enterprise Server system overview. The current sentence about the Ubuntu 20 (Focal Fossa) base operating system was written before Ubuntu 20.04 reached the end of standard support, so it still reads in the future tense, uses the phrase "extended security maintenance" instead of the correct product name, and states no end date.

Old:

Although Ubuntu 20 (Focal Fossa) will reach the end of standard support by May 2025, we will be able to use extended security maintenance and get security support beyond 2025.

New:

Although Ubuntu 20 (Focal Fossa) reached the end of standard support in May 2025, we use Expanded Security Maintenance (ESM), which provides security support through May 2030.

Why

• Ubuntu 20.04 LTS reached the end of standard security maintenance on 2025-05-31.
• Canonical's Ubuntu release cycle lists Expanded Security Maintenance for Ubuntu 20.04 running through May 2030.
• Expanded Security Maintenance (ESM) is the correct Canonical product name (the previous wording said "extended").

Versioning

Every currently supported documentation version (3.17 through 3.21) was released after May 2025, so the corrected wording applies to all built versions and no ifversion conditional is needed. Deprecated versions are archived separately and are unaffected.

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Table of review links

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The table shows the files in the content directory that were changed in this pull request. This helps you review your changes on a staging server. Changes to the data directory are not included in this table.

Source	Review	Production	What Changed
admin/overview/system-overview.md	ghes@ 3.21 3.20 3.19 3.18 3.17	ghes@ 3.21 3.20 3.19 3.18 3.17

Key: fpt: Free, Pro, Team; ghec: GitHub Enterprise Cloud; ghes: GitHub Enterprise Server

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[ThatStoney]

Confirming this was unintentional: I opened it against the public github/docs mirror by mistake. The change belongs in the internal github/docs-internal repository, where I have reopened it. No sensitive information was disclosed. The only change is a one-line wording correction to the already-public Ubuntu 20.04 base OS support statement in the system overview. Closing this and deleting the source branch.