I confirm you that after remove drive from UI, file "/etc/fstab" must be edited: you have to delete all references of the drive(s) you want to remove... in this case the line
/dev/proxvg/proxvz /media/vz ext4 defaults,errors=remount-ro 0 2
Thank you very much for your support!
I mean to remove it from proxomox. I already did it, but it didn't work: when I physically disconnect the harddisk and I reboot Proxmox, it doesn't start and shows this error.