Update app.py

updating the doc string

app.py

@@ -16,6 +16,7 @@ def protein_intake_calculator(fullname:str, weight:int, metric:str)-> str: #it's
     Args:
         fullname: the first argument that takes in a user's full name, so first and last name
         weight: the second argument that takes the input weight of a user. 
+        metric: the third argument that takes the input metric of a user. 
     """
     try:
         # Check which metric the weight is using