bootloader-config: Install grub-efi instead of grub-efi-amd64

@jcc: Hello Jonathan, could you merge this? It will allow grub-efi to install on arm64 as well.

During the mini Debconf in Hamburg, I worked with ema together, and this will allow for Calamares on an arm64 live image

merged

mentioned in commit 401de543

mentioned in commit rclobus-guest/live-build@f2e750e6

mentioned in merge request live-build!352 (merged)

mentioned in commit rclobus-guest/live-build@022b0c58