Fixed wrong type hint

Author: karkkieila

data/part-9/1-objects-and-references.md

@@ -124,7 +124,7 @@ You may remember that lists do not contain any objects themselves. They contain
 
 ```python
 class Product:
-    def __init__(self, name: int, unit: str):
+    def __init__(self, name: str, unit: str):
         self.name = name
         self.unit = unit