Open other app with deeplink isn's in new window & can't back cur app

# Bug Report
## Problem
I have 2 app using deeplink :
App1 : com.te.testApp1://host1.com
App2 : com.et.testApp2://host2.com

from App1 : use InAppBrowser to open App2 with link com.et.testApp2://host2.com

### What is expected to happen?
App1 will open App2 in new window and keep in other window
Can back to App1
Have 2 window

### What does actually happen?
App1 is overwrite by App2 and can't back to App1
Can't back to App1
Have 1 window

but from App1 : use InAppBrowser to open "fb://profile" then open in other app is Facebook and can back to App1

## Information
### Command or Code
import { InAppBrowser } from '@ionic-native/in-app-browser/ngx';
...
(new InAppBrowser).open("com.et.testApp2://host2.com", "_system");

### Environment, Platform, Device
android-targetSdkVersion = 23
Android device 6.0.1

### Version information
ionic 4
angular 7
cordova-android 8
@ionic-native/deeplinks ^5.6.0
@ionic-native/in-app-browser ^5.6.0

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

Start at the InAppBrowser.open entry point with the "_system" target and reproduce the custom deeplink flow on Android 6.0.1 using the reported Cordova, Ionic, and plugin versions. Compare it with the working "fb://profile" flow and verify that App2 opens separately while App1 remains available for back navigation.

Written by the indexing model from the issue text.