Remove UnifiedPeoplePicker code from react-experiments

[litong2]

trafficstars

Remove experimentation

[fabricteam]

📊 Bundle size report

_{🤖 This report was generated against 38bc695b4421eb3c282ce074329e2f6fb1e74e1f}

[codesandbox-ci[bot]]

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Sandbox	Source
@fluentui/react 8 starter	Configuration
@fluentui/react-components 9 starter	Configuration

[fabricteam]

🕵 fluentuiv8 No visual regressions between this PR and main

[layershifter]

_Closing for housekeeping 🏡 Feel free to re-open 👍 _