Fix type hint

Author: Jegarde

src/recnetpy/managers/image_manager.py

@@ -27,7 +27,7 @@ async def get(self, name: str) -> Optional['Image']:
         return None
 
 
-    async def get_many(self, names: List[str]) -> Optional['Image']:
+    async def get_many(self, names: List[str]) -> List['Image']:
         """
         Gets a list of images by a list of image names, and returns 
         a list of image object.