modelData not listModelData

[bri12415]

This was mistakenly done by me from https://github.com/Esri/arcgis-maps-sdk-toolkit-qt/pull/605. I had thought that the data structure being referred to by controller.clientCertificateInfos was one of our ListModels, but it is not. It is just a QStringList, so we can use the modelData keyword.

Before:

After:

Thanks @ldanzinger for pointing this out.

[ldanzinger]

@bri12415 if you haven't done so already, it might be worth a scan to see if there's other areas where we made the same error?

[bri12415]

@ldanzinger will do

Edit: I double checked, it looks like anywhere else we utilize the listModelData role it is in the context of a ListModel