align UUID reducer examples with allowed signatures

[GEFNENEN]

Description of Changes

• Corrected UUID v4/v7 reducer documentation examples to use valid reducer signatures returning ()/Result<(), E>

API and ABI breaking changes

• None

Expected complexity level and risk

• 1 (doc example corrections only)

Testing

• Not run (docs-only change)
• Please review documentation formatting and correctness

[Copilot]

Pull request overview

This pull request updates the UUID reducer documentation examples to align with the valid reducer signatures (() or Result<(), E>). The changes ensure the example function signatures match the allowed return types for reducers.

Changes:

• Updated UUID v4 reducer example to return () instead of Uuid
• Updated UUID v7 reducer example to return Result<(), Box<dyn std::error::Error>> instead of Result<Uuid, ...>
• Added Ok(()) return statement to complete the UUID v7 example

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[CLAassistant]

All committers have signed the CLA.

[bfops]

Thank you for opening a PR to fix this! I had one comment but otherwise LGTM.