plan: rename calculate_rates as required_rates

plan.py

@@ -21,7 +21,7 @@ def basic_rate(recipe: Dict) -> Fraction:
         )
 
 
-def calculate_rates(
+def required_rates(
         recipes: satisfactory.Cookbook,
         remain: List[Dict[str, Fraction]]
 ) -> Dict[str, Fraction]:
@@ -78,7 +78,7 @@ def main():
     # Create an initial name:rate request for all of the target items, then
     # create a plan for their creation.
     remain = [{n: basic_rate(recipes[n]['recipes'][0]) for n in targets}]
-    required_items = calculate_rates(recipes, remain)
+    required_items = required_rates(recipes, remain)
 
     # Note if any particular item is (in aggregate) going to exceed the
     # highest conveyor belt capacity.