VM creation assistant screenshot needs to be updated for GNOME 44
From https://gitlab.gnome.org/GNOME/gnome-boxes/-/blob/main/data/org.gnome.Boxes.appdata.xml.in#L41-43
<screenshot>
<image>https://gitlab.gnome.org/GNOME/gnome-boxes-logos/-/raw/master/screenshots/gnome-42/04-vm-creation-assistant.png</image>
</screenshot>