Try the new and old libxfce4ui gir file name

- Since libxfce4ui 4.15.7, the gir name as been renamed from
  libxfce4ui-2.gir to Libxfce4ui-2.gir
- Add support for both names
- See xfce/libxfce4ui!22
1 job for !9 with libxfce4ui-change in 9 seconds (queued for 1 second)
merge request