Change StartupWMClass to com.borgbase.Vorta (#2536)

Fixes issue #2535

Signed-off-by: gpenz <gpenz@noreply.com>
Co-authored-by: Manu <3916435+m3nu@users.noreply.github.com>

Author: gpenz

src/vorta/assets/metadata/com.borgbase.Vorta.desktop

@@ -6,4 +6,4 @@ Type=Application
 Icon=com.borgbase.Vorta
 Categories=Utility;Archiving;Qt;
 Keywords=borg;
-StartupWMClass=python3
+StartupWMClass=com.borgbase.Vorta