Fix "Running on device" in RNTester README (#32169)

Summary:
Fix broken link
## Changelog

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[CATEGORY] [TYPE] - Message

Pull Request resolved: https://github.com/facebook/react-native/pull/32169

Reviewed By: yungsters

Differential Revision: D30809096

Pulled By: GijsWeterings

fbshipit-source-id: b600e411c7292ba840e076d68f66cb3043887335