feat(costs): Correct cost of Knotted Humeri

Knotted Humeri were less useful in the past, so setting their cost to
zero reflected the tendency to have an overabundance of them. They've
become more practical over time, however, so the cost now assumes you go
out of your way for them.

bonemarketsolver/data/costs.py

@@ -136,10 +136,6 @@ class Cost(Enum):
     # Brawling for yourself, large Bone Market crate, 12 at a time
     JURASSIC_FEMUR = (10*ACTION)/12
 
-    # Knotted Humerus
-    # These are accumulated while acquiring other qualities.
-    KNOTTED_HUMERUS = 0
-
     # Nevercold Brass Sliver
     NEVERCOLD_BRASS = 1
 
@@ -235,6 +231,10 @@ class Cost(Enum):
     # Results of Excavation, 6 at a time
     HELICAL_THIGH = (2*PALAEONTOLOGICAL_DISCOVERY)/6
 
+    # Knotted Humerus
+    # Results of Excavation, 4 at a time
+    KNOTTED_HUMERUS = (2*PALAEONTOLOGICAL_DISCOVERY)/4
+
     # Leviathan Frame
     # Results of Excavation
     LEVIATHAN_FRAME = 25*PALAEONTOLOGICAL_DISCOVERY