removes Mineshaft loading legacy as we had pre 1.13.2 to avoid managing
that very large data file from legacy systems.
Previous to 1.13.2 these data files were never loaded to begin with, so they
effectively do not contain valid/relevant data.
These files take a long time to convert on large worlds and crashes the server.
Additionally, cache the result of a file being missing so we don't keep spam checking it.
