Remove the deprecated keys from desktop file

Remove the deprecated keys causing the .desktop file to fail validation:

```
./data/desktop/org.xfce.Parole.desktop: warning: key "OnlyShowIn" in group "Desktop Action Play" is deprecated
./data/desktop/org.xfce.Parole.desktop: warning: key "OnlyShowIn" in group "Desktop Action Previous" is deprecated
./data/desktop/org.xfce.Parole.desktop: warning: key "OnlyShowIn" in group "Desktop Action Next" is deprecated
```