github_packages: convert formula version to a string in schema

[botantony]

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Another attempt to fix bottle publishing after adding the typecheck.

[Copilot]

Pull request overview

This PR fixes a typecheck error in the GitHub Packages bottle upload functionality by converting a Version object to a string before including it in OCI image annotations.

Key Changes

• Adds .to_s conversion to the version object when setting the org.opencontainers.image.version annotation
• Includes an explanatory comment noting that the schema accepts strings for version

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[carlocab]

Alternatively we should consider reverting #21192 and just fixing the signatures.

[MikeMcQuaid]

Thanks @botantony!