Update Prerequisites section to include free Copilot plans

[jBarrineau]

GitHub Copilot generated this pull request.

Updates the Prerequisites section in the Getting Started guide to clarify that both free and paid GitHub Copilot plans are supported, rather than only paid plans.

[github-actions]

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Table of review links

Note: Please update the URL for your staging server or codespace.

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
copilot/how-tos/github-copilot-app/getting-started.md	fpt ghec	fpt ghec

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

🤖 This comment is automatically generated.

[Sharra-writes]

@jBarrineau Checking to make sure this is true, and I'll let you know what I hear.

[github-actions]

Thanks for opening a pull request! We've triaged this issue for technical review by a subject matter expert 👀