[react-native]Picker.style expects TextStyle (#41729)

The package itself says it's expecting a `TextStyle`, not a `ViewStyle` (https://github.com/facebook/react-native/blob/84adc85523770ebfee749a020920e0b216cf69f8/Libraries/Components/Picker/Picker.js#L62). 

Specifically, setting this to `ViewStyle` causes Typescript to complain if you try to set a `color` property, which does in fact work.

types/react-native/index.d.ts

@@ -2952,7 +2952,7 @@ export interface PickerProps extends PickerPropsIOS, PickerPropsAndroid {
      */
     selectedValue?: any;
 
-    style?: StyleProp<ViewStyle>;
+    style?: StyleProp<TextStyle>;
 
     /**
      * Used to locate this view in end-to-end tests.