Patches floralrat's Clay Casting mod to use the correct amount of liquid clay in barrels for brick casts.

When filling brick casts in a barrel the mod requires there to be at least 15 liquid clay in the barrel but only consumes 5 when actually filling the cast.  I assume this was a typo where the 15 consumed was accidentally typed as 5.

This patch corrects that so filling brick casts consumes 15 litres of the appropriate liquid clay.