docs/Linux-CI: remove old information

[cho-m]

Also added:

• libstdc++ versioning as it isn't aligned to main GCC package
• Ubuntu 26.04 information based on current Resolute data
  • https://packages.ubuntu.com/resolute/gcc
  • https://packages.ubuntu.com/resolute/libstdc++6
  • https://packages.ubuntu.com/source/resolute/glibc

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[Copilot]

Pull request overview

Updates the Linux CI documentation to remove outdated historical notes and refresh the “Past and next versions” guidance for Ubuntu LTS releases used for Homebrew Core bottling.

Changes:

• Updates last_review_date to 2026-03-19.
• Replaces the older Ubuntu version history section with a new table including a libstdc++ column and updated 22.04–28.04 rows.
• Adds Ubuntu 26.04 (Resolute-based) version details to the table.

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[MikeMcQuaid]

Thanks!