Fix faulty layout implementation of preauth hint

[cmaier]

The hint was already there, all the time - just overlayed by the webview due to improper view implementation. That has been fixed.

APPS-1605

How to test?

• Integrate this branch into an app that's got PAYONE as payment provider and check if the preauth hint occurs, if a preauth is configured.
• Check within the sample app if the hint still works for FiServ, which is configured for the sample project.

Definition of Done

• Issue is linked
• All requirements of the issue are fulfilled
• Changelog is updated
• Documentation is updated
• Self-Review
• Review with the Product Owner (Release-Variante o. Minified Build)

App Tests

• Minified build has been tested (aka. Release Build)
• Environments have been taken care of (Production/Staging)
• Supported languages have been tested
• Light-/Dark-Mode has been tested
• Edge-Cases have been tested
• Android API Levels have been taken care of (minSdk?)

Testing

• Tests have been written (aka Unit-Tests, Integration-Tests, ...)