Docs: React Native manual iOS setup instructions need updating

[brainbicycle]

Thanks for making flipper!

After flipper was removed by default from newer react native versions:
https://reactnative.dev/blog/2024/04/22/release-0.74#removal-of-flipper-react-native-plugin

It became less obvious how to integrate flipper into a react native project. The current docs on react native still point to using the
use_flipper method in Podfiles which no longer exists: https://fbflipper.com/docs/getting-started/react-native-ios/

Flipper is still very useful as there are plugins that do not exist yet on either the new dev tools or alternatives, for example relay and performance dev tools (with history).

It would be good to call out at the top of these docs that this no longer works and point to integration doc for generic iOS applications, or ideally more specific up to date docs for react native apps: https://fbflipper.com/docs/getting-started/ios-native/