Live restore is still under development, and 8.1 has branched off of develop in the mean time. This means anyone trying to test live restore on the 8.1 branch is using out of date code.

We likely won't backport the changes to 8.1, so we can just disable live restore on that branch. To do this we need a check in the live restore config logic that disables the config for WiredTiger versions 8.1 and below. There is no live restore code on the 8.0 branch so we don't need to update this config when we do the 8.0 backport