Remove var in /Libralies/Experimental/IncrementalPresenter.js (#22144)

Summary:
Remove `var` declaration keyword in ` /Libralies/Experimental/IncrementalPresenter.js` .

- [x] Check `npm run flow`
- [x] Check `npm run flow-check-ios`
- [x] Check `npm run flow-check-android`
- [x] Check `npm run lint`

[GENERAL] [ENHANCEMENT] [Libralies/Experimental] - remove `var`
Pull Request resolved: https://github.com/facebook/react-native/pull/22144

Differential Revision: D12930731

Pulled By: TheSavior

fbshipit-source-id: 64d7689ffec1da14479bdd7106fdea9a3dbeaa42

Libraries/Experimental/IncrementalPresenter.js

@@ -68,14 +68,15 @@ class IncrementalPresenter extends React.Component<Props> {
     this.props.onDone && this.props.onDone();
   }
   render() {
+    let style: ViewStyleProp;
     if (
       this.props.disabled !== true &&
       this.context.incrementalGroupEnabled !== false &&
       !this._isDone
     ) {
-      var style = [this.props.style, {opacity: 0, position: 'absolute'}];
+      style = [this.props.style, {opacity: 0, position: 'absolute'}];
     } else {
-      var style = this.props.style;
+      style = this.props.style;
     }
     return (
       <IncrementalGroup