Fix large title styles

[yogevbd]

On iOS 13, title attributes should be applied on scrollEdgeAppearance as it applied on standardAppearance.
@guyca We need to think about adding more options to control those two states.

Closes #6337

[chrise86]

Sorry @guyca but this still seems to be broken in RNN 6.12.2. Setting the following either directly on a screen's options or in the default options does not work:

largeTitle: {
  color: 'red', // or whatever colour
}

EDIT: it seems this was merged and released in to 7.0.0, all good on there!