Update docs
Since xfce4-settings 4.15.1, exo-preferred-applications
was merged into xfce4-mime-settings
(Default Applications).
The documentation needs to be updated:
https://docs.xfce.org/xfce/exo/preferred-applications
https://docs.xfce.org/xfce/xfce4-settings/mime
I think the first page can have most of its content moved to the second and only mention that since Xfce 4.16 this is part of xfce4-settings. Of course, screenshots need to be retaken.