task: Update `WriteBoot64` against latest changes in `GoboLinuxInstaller`

[fyrak1s]

With the PR gobolinux/Installer#24 changes have been made to the way grub is being installed onto the ESP.

We should update Writeboot64 to reflect these changes.

For reference: gobolinux/Installer#23 (comment)

... WriteBoot64 is an interesting case!! Not only does it have /boot/efi mentions, but It's also using grub-mkstandalone which is interesting, and likely will need amended. I don't recall seeing it used in the Installer, which is puzzling in it's own right!