Another project called “grub-customizer” has replaced it.
To get started:
press Ctrl+Alt+T on keyboard to open the terminal. When it opens, paste the commands below and run one by one:
sudo add-apt-repository ppa:danielrichter2007/grub-customizer
sudo apt-get update
sudo apt-get install grub-customizer
Once done, you’re able to open this tool from the Unity Dash or application menu. Enjoy!