[Merge] ~philroche/livecd-rootfs/+git/livecd-rootfs:bugfix/lp-2061121-snap-preseed-latest into livecd-rootfs:ubuntu/mantic

[Philip Roche]

I was basing my "policy" comment on the comment above the change

> # Or Ubuntu policy default channel latest/stable/ubuntu-$(release_ver)
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https://code.launchpad.net/~philroche/livecd-rootfs/+git/livecd-rootfs/+merge/464199
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