watchtower/blob/justice_kit_test: convert to require
watchtower/blob/justice_kit_test: convert to require

This is also a prepatory step to making
TestJusticeKitRemoteWitnessConstruction parameteried by the blob type so
we can test both anchor and legacy witness construction.

LightningNetwork/lnd,aakselrod/lnd,aakselrod/lnd,LightningNetwork/lnd