Delete "xfce4" from various strings

* Property dialog
* About dialog
* Time's up dialog
2 jobs for !12 with dialog_title in 1 minute and 3 seconds (queued for 6 seconds)
latest detached
Status Name Job ID Coverage
  Build
passed build #20087

00:00:26

 
  Distcheck
passed distcheck #20088

00:00:37