The way i see it, chroot doesn’t see grub*-common shim-signed as arguments for pacman, but rather other commands to execute.
Enclosing the whole pacman command in quotes might do the trick:
sudo chroot "mnt/boot-sav/sdd2" 'pacman -R grub*-common shim-signed'
Or passing the commands separately:
sudo chroot "mnt/boot-sav/sdd2"
pacman -R grub*-common shim-signed
Otherwise, i can forward you to this guide: [How To] Save your Manjaro installation when it breaks