Provide correct link to the Flipper setup guide

[Vandalko]

The old link pointed to https://fbflipper.com/docs/features/react-native/ which seems to describe 3rd-party plugin integration with Flipper.

At the same time, the new link https://fbflipper.com/docs/getting-started/react-native/ describes how to "Set up your React Native App".

[netlify[bot]]

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