iOS: scrollbar shows after use plugin

# Bug Report

## Problem

Hi,

I recently update the plugin's version to `v4.0.0` to try https://github.com/apache/cordova-plugin-inappbrowser/issues/623, that is closed.

But, I'm observing that after the InApp's instance appear, the "default" scrollbar starts to show (I left a `.zip` with two videos, one with the `v3.2.0`, and another one with the `v4.0.0`) on `iOS 13.5`.

Could be the plugin be interfering with the Ionic's Webview plugin or with the platform detection?

Thank you in advance; let me know if I could help with something.

Zip with the videos: [scrollbar-issue.zip](https://github.com/apache/cordova-plugin-inappbrowser/files/4803543/scrollbar-issue.zip)

### Version information

```
Ionic:

Ionic CLI : 5.4.13
Ionic Framework : @ionic/angular 5.1.1
@angular-devkit/build-angular : 0.901.7
@angular-devkit/schematics : 9.1.7
@angular/cli : 9.1.7
@ionic/angular-toolkit : 2.2.0

Cordova:

Cordova CLI : 9.0.0 (cordova-lib@9.0.1)
Cordova Platforms : ios 5.1.1
Cordova Plugins : cordova-plugin-ionic-keyboard 2.2.0, cordova-plugin-ionic-webview 5.0.0, (and 24 other plugins)

Utility:

cordova-res (update available: 0.15.0) : 0.14.0
native-run : 1.0.0

System:

ios-deploy : 1.10.0
ios-sim : 8.0.2
NodeJS : v12.16.1 (/Users/rricamar/.nvm/versions/node/v12.16.1/bin/node)
npm : 6.14.4
OS : macOS Catalina
Xcode : Xcode 11.5 Build version 11E608c
```

## Checklist

- [x] I searched for existing GitHub issues
- [x] I updated all Cordova tooling to most recent version
- [x] I included all the necessary information above

Start by reproducing the scrollbar behavior on iOS 13.5 with the reported Ionic, Cordova, and plugin versions, using the linked videos and comparing v3.2.0 with v4.0.0. Investigate whether the InAppBrowser plugin interacts with the Ionic WebView or platform detection; done means the default scrollbar no longer appears unexpectedly after the InAppBrowser instance opens.

Written by the indexing model from the issue text.