Setting up Git: Update ChromeOS Git installation to use apt instead of DigitalOcean

[frrst-ian]

Because

The ChromeOS Git installation instructions used an outdated DigitalOcean workaround that is no longer necessary since ChromeOS Linux Development Environment now supports standard package management.

This PR

• Updates ChromeOS section to use apt install git instead of DigitalOcean guide
• Keeps ChromeOS as separate section
• Removes support for older Chromebooks without Linux Dev Environment
• Includes Google Support link for enabling Linux on ChromeOS

Issue

Closes #28232

Additional Information

I have been using ChromeOS for 2 years and can confirm that the Linux Development Environment now supports standard package management, making the DigitalOcean workaround unnecessary. The apt install git method works reliably on current ChromeOS versions with Linux Dev Environment enabled.

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Main review is for installations maintainers - dismissing to prevent blocking