[BUG] Repository creation as archived would fail

[deiga]

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Before the change?

• Creating a new github_repository resource with archived = true and visibility = "private" would fail with 403
• Docs stated that unarchiving a repository via API wasn't supported

After the change?

• Creating a new github_repository resource with archived = true will "stop" execution in Create to only set archived on the repo.
• Docs updated to show that unarchiving is supported

Pull request checklist

• Schema migrations have been created if needed (example)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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[github-actions]

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