The new task fixJarForReobf was added after shadowJar, but since
reobfJar's input is changed in this patch, that new task needs to be
referenced instead of shadowJar.
having spoken to mojang about this the general issue is data which shouldn't
have been saved in the first place, so if we lose this data it's not really
an issue, bar being annoying spammy. if the spam gets on your nerves, shamefully,
all you can really do is forceUpgrade to get the conversions of the way.
Dropping as this breaks other aspects of the server and bar being spammy
seems to have no other real negative outcomes