enable on actual unstable gnome-shell (3.15.3)

data/metadata.json.in

@@ -2,7 +2,7 @@
 "uuid": "@uuid@",
 "name": "Panel OSD",
 "description": "Configuring where on the (main) screen notifications will appear, instead of just above the message tray",
-"shell-version": [ "3.6", "3.8", "3.10", "3.12", "3.14" ],
+"shell-version": [ "3.6", "3.8", "3.10", "3.12", "3.14", "3.15.3" ],
 "localedir": "@LOCALEDIR@",
 "url": "@url@"
 }