Fix volume categories for acre-feet conversions

migrate.py

@@ -55,6 +55,8 @@ def split_conversion_name(name):
 
 def guess_category(name):
     name_l = name.lower()
+    if any(x in name_l for x in ['acre-foot', 'acre-feet', 'acrefoot', 'acre feet']):
+        return 'volume'
     if 'temp scale' in name_l or 'newton (temp' in name_l:
         return 'temperature'
     if any(x in name_l for x in ['force', 'torque', 'newton', 'dyne', 'foot-pound']): return 'force'