Remove var in Libraries/Component (#22020)

Summary:
I removed `var` in Libraries/Component.

- [x] npm run prettier
- [x] npm run flow-check-ios
- [x] npm run flow-check-android

[GENERAL] [ENHANCEMENT] [Libraries/Component] - remove `var`
Pull Request resolved: https://github.com/facebook/react-native/pull/22020

Differential Revision: D12843058

Pulled By: TheSavior

fbshipit-source-id: 90723f3905191cbd29cb18474c700ac65f2503cd

Libraries/Components/RefreshControl/RefreshControl.js

@@ -20,15 +20,16 @@ const nullthrows = require('nullthrows');
 import type {ColorValue} from 'StyleSheetTypes';
 import type {ViewProps} from 'ViewPropTypes';
 
+let RefreshLayoutConsts;
 if (Platform.OS === 'android') {
   const AndroidSwipeRefreshLayout = require('UIManager').getViewManagerConfig(
     'AndroidSwipeRefreshLayout',
   );
-  var RefreshLayoutConsts = AndroidSwipeRefreshLayout
+  RefreshLayoutConsts = AndroidSwipeRefreshLayout
     ? AndroidSwipeRefreshLayout.Constants
     : {SIZE: {}};
 } else {
-  var RefreshLayoutConsts = {SIZE: {}};
+  RefreshLayoutConsts = {SIZE: {}};
 }
 type NativeRefreshControlType = Class<NativeComponent<RefreshControlProps>>;