simplify the recipes in the common case where only 1 of an input is needed

modular-recipes/recipes/peristaltic-pump/pump_housing_front_with_stepper.toml

@@ -1,10 +1,10 @@
 [outputs]
-pump_housing_front_with_stepper={quantity={amount=1}}
+pump_housing_front_with_stepper={}
 
 [inputs]
-pump_housing_front={version=0.1, quantity={amount=1}}
+pump_housing_front={version=0.1}
 m4_5_shcs={quantity={amount=2}, description="M4x5 SHCS"}
-stepper_28byj_48={quantity={amount=1}}
+stepper_28byj_48={}
 
 [dependencies]
 tools = [ "3 mm hex driver" ]