Skip the implicit trailing `.` in `HumanReadableName`'s domain

Skip the implicit trailing `.` in `HumanReadableName`'s domain

Domain names implicitly have a trailing `.`, which we require in
bLIP 32 but generally shouldn't be exposing to the user in
`HumanReadableName`s (after all, they're human-readable). Here we
make sure the trailing `.` is dropped in `HumanReadableName`s
before we re-add them when building the bLIP 32 messages.