window: Set correct default icon name

With the switch to Meson the default icon name is now org.gnome.Music.
Fixes the icon not showing in gnome-control-center.


(cherry picked from commit eeea5f41)
3 jobs for cherry-pick-eeea5f41 in 14 minutes and 48 seconds (queued for 20 seconds)
Status Name Job ID Coverage
  Check
passed pep8 #31137

00:01:15

passed pyflakes #31136

00:11:44

 
  Build
passed build #31138

00:03:03