remove the window entry in grub 2 screen

1) open a /etc/default/grub file

2) add the following line

GRUB_DISABLE_OS_PROBER=true

3) execute update-grub2

Generating grub.cfg ...
Found background image: /usr/share/images/desktop-base/desktop-grub.png
Found linux image: /boot/vmlinuz-2.6.32-5-amd64
Found initrd image: /boot/initrd.img-2.6.32-5-amd64
done