refactor: switch to fade animation for header by default

packages/stack/example/src/SimpleStack.js

@@ -1,10 +1,7 @@
 import * as React from 'react';
 import { Dimensions, Button, View, Text } from 'react-native';
 import { withNavigation } from '@react-navigation/core';
-import {
-  createStackNavigator,
-  TransitionPresets,
-} from 'react-navigation-stack';
+import { createStackNavigator } from 'react-navigation-stack';
 
 const Buttons = withNavigation(props => (
   <React.Fragment>
@@ -151,7 +148,5 @@ export default createStackNavigator(
   },
   {
     initialRouteName: 'List',
-    headerMode: 'screen',
-    ...TransitionPresets.WipeFromBottomAndroid,
   }
 );