Use RTL in RTLExample when Platform != android (#28742)

Summary:
This change upstreams a small change we did in react-native-windows to allow the RTLExample RNTester page to function correctly on Windows.  The change is part of this Pr:
https://github.com/microsoft/react-native-windows/pull/4683
Currently the direction property is gated behind a check for Platform == 'iOS', which means it only works on iOS.  Windows supports direction = 'rtl' so I've chanced this check to Platform != 'android'.

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[Internal] [Changed] - Changed RTLExample RNTester page to use direction = 'rtl' when Platform is not Android.
Pull Request resolved: https://github.com/facebook/react-native/pull/28742

Test Plan: Confirmed this change works correctly in RNTester on Windows.  Have not confirmed iOS as I don't have Mac hardware.

Differential Revision: D21235579

Pulled By: shergin

fbshipit-source-id: 47ab93c2bcd0dbc8347c6746081ae3c64f88faa5

RNTester/js/examples/RTL/RTLExample.js

@@ -521,7 +521,7 @@ const BorderExample = withRTLState(({isRTL, setRTL}) => {
 });
 
 const directionStyle = isRTL =>
-  Platform.OS === 'ios' ? {direction: isRTL ? 'rtl' : 'ltr'} : null;
+  Platform.OS !== 'android' ? {direction: isRTL ? 'rtl' : 'ltr'} : null;
 
 const styles = StyleSheet.create({
   container: {