Remove unused required config values from payment layoutset.

### Description
The studio team has had trouble explaining why some fields needs to be set while creating a UI for configuring payment.
Specifically the field "dataModel" in layout-sets.json should at least be optional, since you in most cases will not use any data from a datamodel directly in you layout. This property is per now required in order to avoid crashing the app.

### Additional Information

The property was first introduced for payment as a result of re-using the config and process handling from the data-task.

### Tasks

_No response_

### Acceptance Criterias

_No response_

Start by locating the payment layout-set configuration in layout-sets.json and trace where dataModel is treated as required. Check the related payment configuration handling and existing tests, then verify that layouts without a dataModel no longer cause the app to crash while layouts that use one still work.

Written by the indexing model from the issue text.