Needed `zpool labelclear -f` on all disks to clear a botched earlier attempt

[sonologic]

@rlaager, I have the following issue with the Debian Bookworm Root on ZFS HOWTO:

I was trying to install debian with zfs on root following the guide on a dedicated server with two disks at OVHCloud, but the result was a system that boots into rescue mode, because it detects two bpool pools. This is likely the result of a mistake I made in an earlier attempt. To resolve it, I had to zpool labelclear -f ${DISK1} and zpool labelclear -f ${DISK2}. Might be good to add this to the 'If you are re-using a disk, clear it as necessary' section.