Fix formatting in iOS prebuild header docs

Summary:
Apply the repository formatter to the iOS prebuild header documentation. This restores the expected Markdown line wrapping and the public format check.

Changelog: [Internal]

bypass-github-export-checks

___

Differential Revision: D121797341

Author: cortinico

packages/react-native/scripts/ios-prebuild/__docs__/headers-rules.md

@@ -246,8 +246,8 @@ of module `React`, closing a cycle:
 React -> ReactNativeHeaders_react -> React
 ```
 
-Found empirically: `react/timing/primitives.h` -> `<React/Debug.h>`. This is
-the same two-module-ownership failure as `UMBRELLA_CXX_GUARDED_EXCLUSIONS`
+Found empirically: `react/timing/primitives.h` -> `<React/Debug.h>`. This is the
+same two-module-ownership failure as `UMBRELLA_CXX_GUARDED_EXCLUSIONS`
 (`RCTFrameTimingsObserver.h`, which reaches the same `primitives.h`), in the
 opposite direction. They are `objc-blocked` by construction (they re-export
 their module's C++ surface), so they were never R4 umbrella or R5 module