.osx: Don’t reset the desktop wallpaper when resetting Launchpad

Files like `530142A0-6AEC-4921-A3A7-7C2B72FFF6E3.db` and `desktoppicture.db` exist in `~/Library/Application\ Support/Dock`, so let’s add a `-` with a wildcard `*` to both sides to ensure we don’t delete `desktoppicture.db` and reset the desktop wallpaper.

Closes #370.