WallpaperCropper: fix lockscreen wallpaper "Set wallpaper" string

The string is wrong and does not reflect the correct action the user is
about to apply.

Change-Id: I91eba87a38546563d6cf88138a0ed07219ec794f
Signed-off-by: Roman Birg <roman@cyngn.com>
Merge "WallpaperCropper: fix lockscreen wallpaper "Set wallpaper" string" into du44