fix: Screen reader event name on RNTester AccessibilityExample (#32926)

Summary:
Fix an issue in the AccessibilityExample on RNTester where the `Screen Reader` item would listen for the `reduceMotionChanged` event instead of the `screenReaderChanged` event

## Changelog

[General] [Fixed] - Fix screen reader event name on RNTester AccessibilityExample

Pull Request resolved: https://github.com/facebook/react-native/pull/32926

Test Plan:
1. Build iOS app
2. Navigate to the Accessibility page
3. Switch over to settings and change VoiceOver at `Settings>Accessibility>VoiceOver>VoiceOver`
4. Switch back to the app and see the results

https://user-images.githubusercontent.com/11707729/150266745-6a9eb547-00a7-4b94-bf19-b8d6e6f76122.mp4

Reviewed By: kacieb

Differential Revision: D33681780

Pulled By: cortinico

fbshipit-source-id: fbd4f3d9ef63997f2b4a40afc8a5adfe6172e525

packages/rn-tester/js/examples/Accessibility/AccessibilityExample.js

@@ -1130,7 +1130,7 @@ class DisplayOptionsStatusExample extends React.Component<{}> {
         <DisplayOptionStatusExample
           optionName={'Screen Reader'}
           optionChecker={AccessibilityInfo.isScreenReaderEnabled}
-          notification={'reduceMotionChanged'}
+          notification={'screenReaderChanged'}
         />
         {isAndroid ? null : (
           <>