Update the Swift Package version automatically

[a-maurice]

Description

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Update the FIREBASE_SPM_VERSION number automatically. Note, this assumes the version number is the same as Cocoapods, which it has consistently been for a while, so should be a valid assumption.

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Testing

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Type of Change

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• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

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[gemini-code-assist]

Code Review

This pull request updates the scripts/update_versions.py script to include logic for updating FIREBASE_SPM_VERSION by reusing the iOS Pod version. The review feedback identifies a potential TypeError if the version retrieval fails and suggests optimizing the script to avoid redundant function calls that perform disk I/O.