Curtin Storage documentation grub_device wrong documented

[Frederik Berg]

In the curtin storage documentation in the disks command section (https://curtin.readthedocs.io/en/latest/topics/storage.html#disk-command), the grub_device attribute is explained. However, this is wrongly documented or not up2date anymore since the code in the curtin repo (https://github.com/canonical/curtin/blob/c66faffeea657c70374479d62fce32965ff7ac31/curtin/commands/curthooks.py#L664) has changed and this behavior is not documented.

How to correct:

Put the grub_device blog in the partition section in the documentation, since the grub_device should be installed on an EFI parition in UEFI mode and not on a device. In the code this is very well documented since it explains that multiple EFI partitions can exist on a device, etc...

Would be nice if this could be simply copied to the documentation. Took me a very long time to figure out the problem until I checked the source code and realized the problem. I guess this is an easy fix which can help others who try to use the new autoinstall.yaml feature of Ubuntu 24.04 :)

Thanks! :)