Update flow Props declaration in TouchableWithoutFeedBack for onFocus and onBlur (#21462)

Summary:
Simple fix to avoid thoses flow error when using Touchables with onFocus & onBlur.

```
Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ src/components/HomeMenu/MenuItem.js:32:8

Cannot create TouchableOpacity element because property onFocus is missing in object type [1] but exists in props [2].

     src/components/HomeMenu/MenuItem.js
      29│   render() {
      30│     const { text, style } = this.props
      31│     return (
 [2]  32│       <TouchableOpacity
      33│         hasTVPreferredFocus
      34│         style={style.item}
      35│         onFocus={() => this.onFocus()}
      36│         onPress={() => Alert.alert(`You pressed ${text}`)}
      37│       >
      38│         <ImageBackground source={separator} style={style.itemBackground}>
      39│           <Text style={style.text}>{text}</Text>
      40│         </ImageBackground>
      41│       </TouchableOpacity>
      42│     )
      43│   }
      44│ }

     node_modules/react-native/Libraries/Components/Touchable/TouchableOpacity.js
 [1] 286│ }): any): React.ComponentType<Props>);
```
Pull Request resolved: https://github.com/facebook/react-native/pull/21462

Differential Revision: D10179260

Pulled By: TheSavior

fbshipit-source-id: e6c5d1136bdde36c8bcbd4df8897a390dcba8e82

Libraries/Components/Touchable/TouchableWithoutFeedback.js

@@ -59,6 +59,8 @@ export type Props = $ReadOnly<{|
   disabled?: ?boolean,
   hitSlop?: ?EdgeInsetsProp,
   nativeID?: ?string,
+  onBlur?: ?Function,
+  onFocus?: ?Function,
   onLayout?: ?Function,
   onLongPress?: ?Function,
   onPress?: ?Function,